Table 2.

Plant characteristics (related to color parameters) and abiotic stressors that influence these parameters.

Name of Color Parameter	Equation	Plant Characteristic/Influencing Factor	Reference
Red coordinate	R	Total chlorophyll content (R2 = 0.08–0.94)	[37,92,94,95,96,98]
		Chlorophyll a (R2 = 0.45) Chlorophyll b (R2 = 0.4) Carotenoids (R2 = 0.45)	[37]
		SPAD (R2 = 0.08–0.92)	[9,83,93,99]
		Plant nitrogen concentration (R2 = 0.91)	[100]
		Leaf nitrogen concentration (R2 = 0.05–0.99)	[91,96]
		Nitrogen fertilization (R2 = 0.69)	[9]
		N-nutrient index (R2 = 0.08–0.95)	[96]
		Nitrogen deficit	[13]
		Fresh biomass (R2 = 0.29–0.76) Dry biomass (R2 = 0.30–0.67)	[101]
		Aboveground biomass (R2 = 0.34–0.82)	[5,6,96,102]
		LAI (R2 = 0.26–0.72)	[101,102]
		Plant height (R2 = 0.17–0.55)	[101]
		Grain yield (R2 = 0.65–0.96)	[3,38]
		Protein content (R2 = 0.65) Oil content (R2 = 0.46) Protein plus oil content (R2 = 0.53) 1000-seed weight (R2 = 0.41)	[53]
		Water deficit	[13]
Green coordinate	G	Total chlorophyll (R2 = 0.22–0.94)	[9,37,91,92,95,96,98]
		Chlorophyll a (R2 = 0.67) Chlorophyll b (R2 = 0.62) Carotenoids (R2 = 0.67)	[37]
		SPAD (R2 = 0.37–0.90)	[9,53,66,83,93,99]
		Leaf nitrogen concentration (R2 = 0.36–0.92)	[91,96]
		Plant nitrogen concentration (R2 = 0.45–0.54) Sap nitrate concentration (R2 = 0.46)	[66]
		Nitrogen fertilization (R2 = 0.69)	[9]
		N-nutrient index (R2 = 0.46–0.98)	[96]
		Nitrogen deficit	[13]
		Canopy biomass (R2 = 0.49–0.72)	[66]
		Aboveground biomass (R2 = 0.59–0.96)	[5,6,96]
		Grain yield (R2 = 0.39–99)	[3,38]
		Protein content (R2 = 0.64) Oil content (R2 = 0.45) Protein plus oil content (R2 = 0.53) 1000-seed weight (R2 = 0.39)	[53]
		Water deficit	[13]
Blue coordinate	B	Carotenoids (R2 = 0.36)	[37]
		SPAD (R2 = 0.04–0.64)	[83,93]
		Plant nitrogen concentration (R2 = 0.89)	[100]
		Protein content (R2 = 0.62) Oil content (R2 = 0.45) Protein plus oil content (R2 = 0.50)	[53]
		Grain yield (R2 = 0.47–0.97)	[3]
		Aboveground biomass (R2 = 0.49)	[6]
		Plant water content (R2 = 0.48)	[102]
		Water deficit	[13]
Normalized red coordinate	$\mathrm{r}=\frac{\mathrm{R}}{\mathrm{R}+\mathrm{G}+\mathrm{B}}$	Total chlorophyll content (R2 = 0.03–0.91)	[94,95,96]
		Chlorophyll a (R2 = 0.74) Chlorophyll b (R2 = 0.67) Total chlorophyll (R2 = 0.74) Carotenoids (R2 = 0.76)	[37]
		SPAD (R2 = 0.03–0.8)	[68,83,92,93,97,99,103]
		Sap nitrate concentration (R2 = 0.78)	[103]
		Plant nitrogen concentration (R2 = 0.48–0.67)	[104,105]
		Shoot nitrogen concentration (R2 = 0.63)	[103]
		Leaf nitrogen concentration (R2 = 0.04–0.99)	[96,105]
		N-nutrient index (R2 = 0.03–0.96)	[96]
		Nitrogen uptake (R2 = 0.34–0.41)	[96]
		Aboveground biomass (R2 = 0.05–0.84)	[6,96,102]
		LAI (R2 = 0.42–0.55)	[102]
		Plant height (R2 = 0.25–0.52)	[102]
		Grain yield (R2 = 0.01–0.94)	[3,4]
		Plant water content (R2 = 0.46–0.62)	[102]
		Water deficit	[13]
Normalized green coordinate	$\mathrm{g}=\frac{\mathrm{G}}{\mathrm{R}+\mathrm{G}+\mathrm{B}}$	Chlorophyll content (R2 = 0.21–0.81)	[96]
		SPAD (R2 = 0.01–0.62)	[83,93,99,103,106]
		Plant nitrogen concentration (R2 = 0.29–0.61)	[69,104,105,106,107]
		Leaf nitrogen concentration (R2 = 0.24–0.99)	[96,105]
		Nitrate concentration of leafstalk (R2 = 0.62)	[106]
		Stem nitrate concentration (R2 = 0.62)	[107]
		Sap nitrate concentration (R2 = 0.68)	[103]
		N-nutrient index (R2 = 0.27–0.94)	[96]
		Shoot nitrogen accumulation (R2 = 0.56)	[108]
		Shoot nitrogen concentration (R2 = 0.68)	[103]
		Inorganic nitrogen in soil (R2 = 0.76)	[106]
		Aboveground biomass (R2 = 0.02–0.79)	[5,69,96]
		Dry mass (R2 = 0.3–0.86)	[108,109,110]
		LAI (R2 = 0.59)	[69,108]
		Plant height (R2 = 0.24–0.44)	[102]
		Grain yield (R2 = 0.3–0.89)	[3,107,109]
Normalized blue coordinate	$\mathrm{b}=\frac{\mathrm{B}}{\mathrm{R}+\mathrm{G}+\mathrm{B}}$	Total chlorophyll content (R2 = 0.01–0.90)	[95,96,102]
		SPAD (R2 = 0.03–0.71)	[68,83,93,97,103]
		Plant nitrogen concentration (R2 = 0.03–0.77)	[102,104,105]
		Leaf nitrogen concentration (R2 0.11–0.69)	[96,105]
		Shoot nitrogen concentration (R2 = 0.55)	[103]
		Sap nitrate concentration (R2 = 0.53)	[103]
		Nitrogen deficit	[13]
		N-nutrient index (R2 = 0.18–0.60)	[96]
		Aboveground biomass (R2 = 0.36–0.57)	[5,6]
		LAI (R2 = 0.03–0.48)	[102]
		Grain yield (R2 = 0.06–0.86)	[3,4]
		Water deficit	[13]
Red–green sum index (RGSI)	$\mathrm{R}\mathrm{G}\mathrm{S}\mathrm{I}=\mathrm{R}+\mathrm{G}$	Total chlorophyll content (R2 = 0.72–0.87)	[92,94]
		SPAD (R2 = 0.57–0.59)	[92,99]
Red–blue sum index (RBSI)	$\mathrm{R}\mathrm{B}\mathrm{S}\mathrm{I}=\mathrm{R}+\mathrm{B}$	Total chlorophyll content (R2 = 0.53)	[92]
		SPAD (R2 = 0.43–0.54)	[92,99]
Normalized red–blue sum index (NRBSI)	$\mathrm{N}\mathrm{R}\mathrm{B}\mathrm{S}\mathrm{I}=\mathrm{r}+\mathrm{b}$	Plant nitrogen concentration (R2 = 0.7) Leaf nitrogen concentration (R2 = 0.7)	[105]
Green–blue sum index (GBSI)	$\mathrm{G}\mathrm{B}\mathrm{S}\mathrm{I}=\mathrm{G}+\mathrm{B}$	SPAD (R2 = 0.42)	[99]
Red-green blue sum index (RGBSI)	$\mathrm{R}\mathrm{G}\mathrm{B}\mathrm{S}\mathrm{I}=\mathrm{R}+\mathrm{G}+\mathrm{B}$	Total chlorophyll content (R2 = 0.71)	[92]
		SPAD (R2 = 0.54–0.64)	[92,99]
Difference BG-R index (DBGRI)	$\mathrm{D}\mathrm{B}\mathrm{G}\mathrm{R}\mathrm{I}=\mathrm{B}+\mathrm{G}-\mathrm{R}$	SPAD (R2 = 0.39)	[92]
Normalized Difference BG-R index (NDBGRI)	$\mathrm{N}\mathrm{D}\mathrm{B}\mathrm{G}\mathrm{R}\mathrm{I}=\frac{\mathrm{B}+\mathrm{G}-\mathrm{R}}{\mathrm{B}+\mathrm{G}+\mathrm{R}}$	Chlorophyll a (R2 = 0.81–0.93) Chlorophyll b (R2 = 0.8–0.93) Carotenoids (R2 = 0.78–0.93) Nitrogen content (R2 = 0.69–0.78)	[44]
Red minus green	$\mathrm{R}\mathrm{M}\mathrm{G}=\mathrm{R}-\mathrm{G}$	SPAD (R2 = 0.56)	[99]
Normalized green minus red index (NGMR)	$\mathrm{N}\mathrm{G}\mathrm{M}\mathrm{R}=\mathrm{g}-\mathrm{r}$	Chlorophyll a (R2 = 0.36–0.62) Chlorophyll b (R2 = 0.33–0.6) Carotenoids (R2 = 0.28–0.56)	[44]
Green minus red index (GMR)	$\mathrm{G}\mathrm{M}\mathrm{R}=\mathrm{G}-\mathrm{R}$	SPAD (R2 = 0.36)	[9]
		Plant nitrogen concentration (R2 = 0.46–0.93)	[69,104]
		Nitrogen fertilization (R2 = 0.48)	[9]
		LAI (R2 = 0.83–0.95)	[69]
		Aboveground biomass (R2 = 0.79–0.93)	[69]
Normalized green minus blue (NGMB)	$\mathrm{N}\mathrm{G}\mathrm{M}\mathrm{B}=\mathrm{g}-\mathrm{b}$	Plant nitrogen concentration (R2 = 0.6) Leaf nitrogen concentration (R2 = 0.6)	[105]
		Total chlorophyll content (R2 = 0.26–0.79)	[95]
Green minus blue (GMB)	$\mathrm{G}\mathrm{M}\mathrm{B}=\mathrm{G}-\mathrm{B}$	Total chlorophyll content (R2 = 0.52–0.96)	[9,95]
		SPAD (R2 = 0.37–0.83)	[9,83]
		Nitrogen fertilization (R2 = 0.77)	[9]
Normalized red minus blue index (NRMB)	$\mathrm{N}\mathrm{R}\mathrm{M}\mathrm{B}=\mathrm{r}-\mathrm{b}$	Total chlorophyll content (R2 = 0.44–0.9)	[95]
Red minus blue index (RMB)	$\mathrm{R}\mathrm{M}\mathrm{B}=\mathrm{R}-\mathrm{B}$	Total chlorophyll content (R2 = 0.44–0.99)	[9,92,95,111]
		Chlorophyll a (R2 = 0.67) Chlorophyll b (R2 = 0.55)	[111]
		SPAD (R2 = 0.32–0.62)	[9,83,92,99,111]
		Leaf nitrogen content (R2 = 0.6)	[111]
		Nitrogen fertilization (R2 = 0.76)	[9]
Green–blue simple ratio (GB)	$\mathrm{G}\mathrm{B}=\frac{\mathrm{G}}{\mathrm{B}}$	SPAD (R2 = 0.18–0.82)	[112]
		Plant nitrogen concentration (R2 = 0.7) Leaf nitrogen concentration (R2 = 0.7)	[105]
		Aboveground biomass (R2 = 0.57)	[5]
Blue–green simple ratio (BG)	$\mathrm{B}\mathrm{G}=\frac{\mathrm{B}}{\mathrm{G}}$	SPAD (R2 = 0.00–0.74)	[83]
		Fresh biomass (R2 = 0.92–0.94) Dry biomass (R2 = 0.74–0.85) LAI (R2 = 0.79–0.94) Plant height (R2 = 0.74–0.90)	[101]
Red–blue simple ratio (RB)	$\mathrm{R}\mathrm{B}=\frac{\mathrm{R}}{\mathrm{B}}$	Plant nitrogen concentration (R2 = 0.00–0.77)	[104,105]
		Leaf nitrogen concentration (R2 = 0.6)	[105]
		Fresh biomass (R2 = 0.77–0.94) Dry biomass (R2 = 0.64–0.90)	[101]
		Aboveground biomass (R2 = 0.47)	[5]
		LAI (R2 = 0.76–0.88) Plant height (R2 = 0.61–0.86)	[101]
Blue–red simple ratio (BR)	$\mathrm{B}\mathrm{R}=\frac{\mathrm{B}}{\mathrm{R}}$	Total chlorophyll content (R2 = 0.09–0.97)	[96,111]
		Chlorophyll a (R2 = 0.6) Chlorophyll b (R2 = 0.45) SPAD (R2 = 0.48)	[111]
		Leaf nitrogen content (R2 = 0.05–0.96)	[36,96,111]
		Total canopy nitrogen content (R2 = 0.55)	[36]
		N-nutrient level (R2 = 0.12–0.92)	[96]
		Aboveground biomass (R2 = 0.48–0.84)	[96]
Green–red simple ratio (GR)	$\mathrm{G}\mathrm{R}=\frac{\mathrm{G}}{\mathrm{R}}$	Total chlorophyll content (R2 = 0.01–0.92)	[94,96]
		Chlorophyll a (R2 = 0.69–0.89) Chlorophyll b (R2 = 0.68–0.89) Carotenoids (R2 = 0.64–0.88)	[44]
		SPAD (R2 = 0.04–0.91)	[68,83,112,113]
		Aboveground biomass (R2 = 0.01–0.85)	[50,69,96]
		LAI (R2 = 0.66–0.93)	[69]
		Plant nitrogen concentration (R2 = 0.55–0.92)	[69,104,105]
		Leaf nitrogen concentration (R2 = 0.12–0.99)	[96,105]
		N-nutrient index (R2 = 0.11–0.95)	[96]
Red–green ratio index (RGRI)	$\mathrm{R}\mathrm{G}\mathrm{R}\mathrm{I}=\frac{\mathrm{R}}{\mathrm{G}}$	Canopy temperature	[54]
		Leaf nitrogen concentration (R2 = 0.7–0.87)	[47,105]
		Plant nitrogen concentration (R2 = 0.1–0.7)	[101,105]
		Flower number (R2 = 0.83)	[52]
Normalized difference red–blue index (NDRBI), (alternative name is Kawashima index, IKAW)	$\mathrm{N}\mathrm{D}\mathrm{R}\mathrm{B}\mathrm{I}=\frac{\mathrm{R}-\mathrm{B}}{\mathrm{R}+\mathrm{B}}$	Total chlorophyll content (R2 = 0.33–0.9)	[94,95,111]
		Chlorophyll a (R2 = 0.59) Chlorophyll b (R2 = 0.44)	[111]
		SPAD (R2 = 0.2–0.84)	[111,112,114,115]
		Leaf nitrogen concentration (R2 = 0.51–0.92)	[47,105,111]
		Plant nitrogen concentration (R2 = 0.6)	[105]
		Aboveground biomass (R2 = 0.48–0.50)	[5,116]
		LAI (R2 = 0.71)	[117]
		Grain yield (R2 = 0.25–0.59)	[114]
Normalized green–blue difference index; normalized difference green–blue index (NGBDI, NDGBI)	$\mathrm{N}\mathrm{G}\mathrm{B}\mathrm{D}\mathrm{I}=\frac{\mathrm{G}-\mathrm{B}}{\mathrm{G}+\mathrm{B}}$	Total chlorophyll content (R2 = 0.29–0.85)	[95]
		SPAD (R2 = 0.00–0.71)	[83]
Normalized green–red difference index (NGRDI)	$\mathrm{N}\mathrm{G}\mathrm{R}\mathrm{D}\mathrm{I}=\frac{\mathrm{G}-\mathrm{R}}{\mathrm{G}+\mathrm{R}}$	Total leaf chlorophyll (R2 = 0.62)	[118]
		Chlorophyll a (R2 = 0.72–0.89) Chlorophyll b (R2 = 0.71–0.89) Carotenoids (R2 = 0.68–0.89)	[44]
		SPAD (R2 = 0.05–0.84)	[83,112,118,119]
		Plant nitrogen concentration (R2 = 0.46–0.79)	[104,105,120]
		Leaf nitrogen concentration (R2 = 0.51–0.87)	[47,105,120]
		Leaf nitrogen accumulation (R2 = 0.5)	[43]
		Aboveground biomass (R2 = 0.39–0.56)	[40,50,116,121]
		Aboveground dry biomass (R2 = 0.3–0.55)	[41]
		Dry biomass (R2 = 0.0–0.92)	[72,122,123]
		Leaf dry matter (R2 = 0.53)	[43]
		LAI (R2 = 0.18–0.74)	[43,102,117,124]
		Surface of an individual plant	[125]
		Vegetation cover (R2 = 0.05–0.81)	[45]
		Stem diameter	[125]
		Plant height (R2 = 0.27–0.53)	[102,125]
		Plant water content (R2 = 0.37–0.50)	[102]
		Grain yield (R2 = 0.26–0.59)	[124]
		Flower number (R2 = 0.83)	[52]
Woebbecke’s indices (WI)	$\mathrm{W}\mathrm{I}=\frac{\mathrm{G}-\mathrm{B}}{|\mathrm{R}-\mathrm{G}|}$	SPAD (R2 = 0.17–0.85)	[112]
Ku’s index (KI)	$\mathrm{K}\mathrm{I}=\frac{\mathrm{R}}{\mathrm{R}-\mathrm{B}}$	Total chlorophyll (R2 = 0.33–0.99)	[9]
Simple ratio intensity R-GB (SRrgb)	$\mathrm{S}\mathrm{R}\mathrm{r}\mathrm{g}\mathrm{b}=\frac{\mathrm{R}}{\mathrm{G}+\mathrm{B}}$	Chlorophyll a (R2 = 0.82–0.93) Chlorophyll b (R2 = 0.81–0.93) Carotenoids (R2 = 0.79–0.93) Leaf nitrogen concentration (R2 = 0.69–0.79)	[44]
Normalized difference index (NDI)	$\mathrm{N}\mathrm{D}\mathrm{I}=\frac{\mathrm{r}-\mathrm{g}}{\mathrm{r}+\mathrm{g}+0.01}$	Chlorophyll a (R2 = 0.72–0.9) Chlorophyll b (R2 = 0.71–0.9) Carotenoids (R2 = 0.67–0.89)	[44]
		Dry mass (R2 = 0.48) LAI (R2 = 0.52) Shoot nitrogen accumulation (R2 = 0.56)	[108]
Soil adjusted vegetation index green (RGB) (SAVIgreen)	${\mathrm{S}\mathrm{A}\mathrm{V}\mathrm{I}}_{\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{n}}=\frac{(1+\mathrm{L})(\mathrm{g}-\mathrm{r})}{\left(\mathrm{g}+\mathrm{r}\right)+\mathrm{L}}$, L = 0.5	Chlorophyll a (R2 = 0.7–0.89) Chlorophyll b (R2 = 0.69–0.88) Carotenoids (R2 = 0.65–0.88)	[44]
Optimized soil adjusted vegetation index green (RGB) (OSAVIgreen)	${\mathrm{O}\mathrm{S}\mathrm{A}\mathrm{V}\mathrm{I}}_{\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{n}}=\frac{1.5·(\mathrm{g}-\mathrm{r})}{\mathrm{g}+\mathrm{r}+0.16}$	Chlorophyll a (R2 = 0.71–0.89) Chlorophyll b (R2 = 0.7–0.89) Carotenoids (R2 = 0.67–0.88)	[44]
Enhanced vegetation index green (RGB) (EVIgreen)	${\mathrm{E}\mathrm{V}\mathrm{I}}_{\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{n}}=\frac{2.5·(\mathrm{g}-\mathrm{r})}{\mathrm{g}+6·\mathrm{r}-7.5·\mathrm{b}+1}$	Chlorophyll a (R2 = 0.81–0.92) Chlorophyll b (R2 = 0.8–0.92) Carotenoids (R2 = 0.79–0.92) Leaf nitrogen concentration (R2 = 0.69–0.77)	[44]
Enhanced vegetation index 2 green (RGB) (EVI2green)	${\mathrm{E}\mathrm{V}\mathrm{I}2}_{\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{n}}=\frac{2.5·(\mathrm{g}-\mathrm{r})}{\mathrm{g}+2.4·\mathrm{r}+1}$	Chlorophyll a (R2 = 0.69–0.89) Chlorophyll b (R2 = 0.68–0.88) Carotenoids (R2 = 0.66–0.88)	[44]
Principal component analysis Pagola’s index (IPCA)	${\mathrm{I}}_{\mathrm{p}\mathrm{c}\mathrm{a}}=0.7582\left|\mathrm{r}-\mathrm{b}\right|-$ $-0.1168\left|\mathrm{r}-\mathrm{g}\right|+0.6414\left|\mathrm{g}-\mathrm{b}\right|$	SPAD (R2 = 0.1–0.88) Grain yield (R2 = 0.35–0.59)	[114]
Principal component analysis Saberioon’s index (IPCAS)	${\mathrm{I}}_{\mathrm{P}\mathrm{C}\mathrm{A}\mathrm{S}}=0.994\left|\mathrm{R}-\mathrm{B}\right|+$ $+0.914\left|\mathrm{G}-\mathrm{R}\right|+0.961\left|\mathrm{G}-\mathrm{B}\right|$	SPAD (R2 = 0.62)	[126]
		Aboveground biomass (R2 = 0.78)	[5]
Red–green fit index (RGFI)	$\mathrm{R}\mathrm{G}\mathrm{F}\mathrm{I}=2·\mathrm{G}-0.924·\mathrm{R}-$ $-44.851-\mathrm{B}$	SPAD (R2 = 0.94)	[119]
Blue–green fit index (BGFI)	$\mathrm{B}\mathrm{G}\mathrm{F}\mathrm{I}=2·\mathrm{G}-\mathrm{R}-$ $-73.645-0.71·\mathrm{B}$	SPAD (R2 = 0.62)	[119]
Normalized excess green index (NExG)	$\mathrm{N}\mathrm{E}\mathrm{x}\mathrm{G}=2·\mathrm{g}-\mathrm{r}-\mathrm{b}$	Canopy-to-air temperature difference (R2 = 0.47–0.8) Crop water stress index (R2 = 0.63–0.8) Canopy temperature (R2 = 0.66–0.73) Leaf water potential (R2 = 0.85–0.87) Sap flow (R2 = 0.62)	[55]
		SPAD (R2 = 0.45)	[126]
		Plant nitrogen concentration (R2 = 0.28–0.68)	[105,120]
		Leaf nitrogen concentration (R2 = 0.26–0.65)	[105,120]
		Aboveground biomass (R2 = 0.47)	[5]
		Fresh biomass (R2 = 0.48–0.88) Dry biomass (R2 = 0.27–0.81)	[101]
		Global primary productivity (GPP)	[46]
		LAI (R2 = 0.09–0.88)	[101,124]
		Surface of an individual plant	[125]
		Vegetation cover (R2 = 0.03–0.77)	[45]
		Plant height (R2 = 0.53–0.69)	[101,125]
		Stem diameter	[125]
Excess green index (ExG)	$\mathrm{E}\mathrm{x}\mathrm{G}=2·\mathrm{G}-\mathrm{R}-\mathrm{B}$	SPAD (R2 = 0.34–0.86)	[83,119]
		Flower number (R2 = 0.58)	[52]
Excess red index (ExR)	$\mathrm{E}\mathrm{x}\mathrm{R}=1.4·\mathrm{g}-\mathrm{r}$	Plant nitrogen concentration (R2 = 0.52–0.72)	[104,105]
		Leaf nitrogen concentration (R2 = 0.7)	[105]
		Leaf nitrogen accumulation (R2 = 0.49)	[43]
		Aboveground biomass (R2 = 0.40–0.56)	[102,116]
		LAI (R2 = 0.16–0.8)	[43,102,117,124]
		Leaf dry matter (R2 = 0.52)	[43]
		Surface of an individual plant Stem diameter	[125]
		Plant height (R2 = 0.26–0.52)	[102,125]
		Plant water content (R2 = 0.40–0.52)	[102]
		Grain yield (R2 = 0.26–0.58)	[124]
Excess blue vegetation index (ExB)	$\mathrm{E}\mathrm{x}\mathrm{B}=1.4·\mathrm{b}-\mathrm{g}$	Aboveground biomass (R2 = 0.57)	[5]
		Plant nitrogen concentration (R2 = 0.7) Leaf nitrogen concentration (R2 = 0.7)	[105]
Normalized excess green minus excess red (ExGR)	$\mathrm{N}\mathrm{E}\mathrm{x}\mathrm{G}\mathrm{R}=\mathrm{N}\mathrm{E}\mathrm{x}\mathrm{G}-\mathrm{N}\mathrm{E}\mathrm{x}\mathrm{R}$	SPAD (R2 = 0.44)	[126]
		Plant nitrogen concentration (R2 = 0.6) Leaf nitrogen concentration (R2 = 0.6)	[105]
		LAI (R2 = 0.09–0.65)	[124]
		Aboveground biomass (R2 = 0.39)	[5]
		Surface of an individual plant Plant height Stem diameter	[125]
Excess green minus excess red (ExGR)	$\mathrm{E}\mathrm{x}\mathrm{G}\mathrm{R}=\mathrm{E}\mathrm{x}\mathrm{G}-\mathrm{E}\mathrm{x}\mathrm{R}$	SPAD (R2 = 0.09–0.72)	[112]
Green leaf index (GLI)	$\mathrm{G}\mathrm{L}\mathrm{I}=\frac{2·\mathrm{G}-\mathrm{R}-\mathrm{B}}{2·\mathrm{G}+\mathrm{R}+\mathrm{B}}$	SPAD (R2 = 0.00–0.79)	[83,118,119,127]
		Total leaf chlorophyll (R2 = 0.64)	[118]
		Leaf nitrogen concentration (R2 = 0.6) Plant nitrogen concentration (R2 = 0.6)	[105]
		Aboveground biomass (R2 = 0.49–0.74)	[5,50]
		Dry biomass (R2 = 0.33–0.36)	[123]
		LAI (R2 = 0.07–0.58)	[124]
		Surface of an individual plant Stem diameter	[125]
		Plant height (R2 = 0.24–0.44)	[102,125]
		Flower number (R2 = 0.37)	[52]
		Water damage in field	[128]
Modified green–red vegetation index (MGRVI)	$\mathrm{M}\mathrm{G}\mathrm{R}\mathrm{V}\mathrm{I}=\frac{{\mathrm{G}}^2-{\mathrm{R}}^2}{{\mathrm{G}}^2+{\mathrm{R}}^2}$	Plant nitrogen concentration (R2 = 0.6) Leaf nitrogen concentration (R2 = 0.6)	[105]
		Aboveground biomass (R2 = 0.40–0.56)	[50,102,116]
		Dry biomass (R2 = 0.53–0.59)	[122]
		LAI (R2 = 0.45–0.80)	[102,117]
		Plant height (R2 = 0.27–0.53)	[102]
		Plant water content (R2 = 0.37–0.48)	[102]
		Flower number (R2 = 0.83)	[52]
Red–green blue vegetation index (RGBVI)	$\mathrm{R}\mathrm{G}\mathrm{B}\mathrm{V}\mathrm{I}=\frac{{\mathrm{G}}^2-\mathrm{R}·\mathrm{B}}{{\mathrm{G}}^2+\mathrm{R}·\mathrm{B}}$	SPAD (R2 = 0.18–0.53)	[112]
		Plant nitrogen concentration (R2 = 0.6) Leaf nitrogen concentration (R2 = 0.6)	[105]
		Fresh biomass (R2 = 0.21–0.55)	[129]
		Dry biomass (R2 = 0.44)	[122]
Color index of vegetation (CIVE)	$\mathrm{C}\mathrm{I}\mathrm{V}\mathrm{E}=0.441·\mathrm{R}-0.881·\mathrm{G}+$ $+0.385·\mathrm{B}+18.78745$	Aboveground biomass (R2 = 0.72)	[5]
		Flower number (R2 = 0.59)	[52]
Color index of vegetation (CIVE)	$\mathrm{C}\mathrm{I}\mathrm{V}\mathrm{E}=0.441·\mathrm{r}-0.881·\mathrm{g}+$ $+0.385·\mathrm{b}+18.78745$	Plant height (R2 = 0.24–0.46)	[102]
Vegetative index (VEG)	$\mathrm{V}\mathrm{E}\mathrm{G}=\frac{\mathrm{G}}{{\mathrm{R}}^{\mathrm{a}}{\mathrm{B}}^{1-\mathrm{a}}}\mathrm{a}=0.667$	SPAD (R2 = 0.17–0.84)	[112]
		LAI (R2 = 0.5–0.8)	[117]
		Aboveground biomass (R2 = 0.4–0.71)	[5,50]
		Flower number (R2 = 0.44)	[52]
True color vegetation index (TCVI)	$$\begin{gathered} \mathrm{T}\mathrm{C}\mathrm{V}\mathrm{I}= \\ =\frac{1.4·2·\left(\mathrm{R}-\mathrm{B}\right)}{2·\mathrm{R}-\mathrm{G}-2·\mathrm{B}+255·0.4} \end{gathered}$$	Leaf nitrogen concentration (R2 = 0.81–0.91)	[47]
Visible atmospherically resistance index (VARI)	$\mathrm{V}\mathrm{A}\mathrm{R}\mathrm{I}=\frac{\mathrm{G}-\mathrm{R}}{\mathrm{G}+\mathrm{R}-\mathrm{B}}$	Total leaf chlorophyll (R2 = 0.61)	[118]
		Chlorophyll a (R2 = 0.78–0.92) Chlorophyll b (R2 = 0.77–0.92) Carotenoids (R2 = 0.75–0.92)	[44]
		Plant nitrogen concentration (R2 = 0.59–0.77)	[104,105]
		Leaf nitrogen concentration (R2 = 0.7–0.89)	[44,47,105]
		Leaf nitrogen accumulation (R2 = 0.61)	[43]
		SPAD (R2 = 0.18–0.75)	[112,118]
		Aboveground biomass (R2 = 0.16–0.62)	[6,50,102,116]
		Leaf dry matter (R2 = 0.64)	[43]
		Dry biomass (R2 =0.57–0.63)	[123]
		LAI (R2 = 0.23–0.77)	[43,102,117,124]
		Surface of an individual plant Stem diameter	[125]
		Plant height (R2 = 0.27–0.52)	[102,125]
		Plant water content (R2 = 0.38–0.52)	[102]
		Grain yield (R2 = 0.28–0.71)	[124]
		Flower number (R2 = 0.81)	[52]
Visible atmospherically resistance index (VARI) by Sakamoto	$\mathrm{V}\mathrm{A}\mathrm{R}\mathrm{I}\mathrm{s}=\frac{\mathrm{G}-\mathrm{R}}{\mathrm{G}+\mathrm{R}}$	Plant length (R2 = 0.23–0.98) Total dry weight (R2 = 0.06–0.97)	[130]
		LAI (R2 = 0.62–0.98)	[130,131]
Combination (COM)	$$\begin{gathered} \mathrm{C}\mathrm{O}\mathrm{M}=0.25·\mathrm{N}\mathrm{E}\mathrm{x}\mathrm{G}+0.3· \\ ·\mathrm{N}\mathrm{E}\mathrm{x}\mathrm{G}\mathrm{R}+ \end{gathered}$$ $+0.33·\mathrm{C}\mathrm{I}\mathrm{V}\mathrm{E}+0.12·\mathrm{V}\mathrm{E}\mathrm{G}$	Aboveground biomass (R2 = 0.72)	[5]
ChOL	$\log \mathrm{s}\mathrm{i}\mathrm{g}\left(\frac{\mathrm{G}-\frac{\mathrm{R}}{3}-\frac{\mathrm{B}}{3}}{255}\right)$	Total chlorophyll content (R2 = 0.48–0.94)	[94,98]
Coordinates of the HSI model	$\mathrm{H}\mathrm{u}\mathrm{e}$	Total chlorophyll content (R2 = 0.71)	[91]
		Leaf nitrogen concentration (R2 = 0.77)	[91]
		Nitrogen deficit Water deficit	[13]
	$\mathrm{S}\mathrm{a}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$	Water deficit	[13]
	$\mathrm{I}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}$	SPAD (R2 = 0.08–0.92)	[83]
		Plant nitrogen concentration (R2 = 0.49–0.76)	[104]
		Nitrogen deficit Water deficit	[13]
		Aboveground biomass (R2 = 0.57)	[5]
Coordinates of the HSB model	$\mathrm{H}\mathrm{u}\mathrm{e}$	Total chlorophyll (R2 = 0.48)	[37]
		Chlorophyll a (R2 = 0.49–0.92) Chlorophyll b (R2 = 0.4–0.92) Carotenoids (R2 = 0.49–0.92)	[37,44]
		SPAD (R2 = 0.65–0.76)	[68]
		Leaf nitrogen concentration (R2 = 0.71–0.79)	[44]
		Protein content (R2 = 0.64) Oil content (R2 = 0.50) Protein plus oil content (R2 = 0.49) 1000-seed weight (R2 = 0.43)	[53]
	$\mathrm{S}\mathrm{a}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$	Total chlorophyll (R2 = 0.77) Chlorophyll a (R2 = 0.77) Chlorophyll b (R2 = 0.71) Carotenoids (R2 = 0.77)	[37]
		Protein content (R2 = 0.69) Oil content (R2 = 0.47) Protein plus oil content (R2 = 0.58) 1000-seed weight (R2 = 0.40)	[53]
	$\mathrm{B}\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s}$	Total chlorophyll (R2 = 0.66) Chlorophyll a (R2 = 0.67) Chlorophyll b (R2 = 0.61) Carotenoids (R2 = 0.66)	[37]
		Protein content (R2 = 0.64) Oil content (R2 = 0.46) Protein plus oil content (R2 = 0.53) 1000-seed weight (R2 = 0.39)	[53]
Dark green color index (DGCI) on basis HSB model	$\mathrm{D}\mathrm{G}\mathrm{C}\mathrm{I}=\frac{\frac{\mathrm{H}\mathrm{u}\mathrm{e}-60}{60}}{3}+$ $+\frac{\left(1-\mathrm{S}\mathrm{a}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\right)}{3}+$ $+\frac{1-\mathrm{B}\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s}}{3}$	Total chlorophyll (R2 = 0.71)	[37]
		Chlorophyll a (R2 = 0.71–0.86) Chlorophyll b (R2 = 0.61–0.86) Carotenoids (R2 = 0.71–0.86)	[37,44]
		SPAD (R2 = 0.16–0.94)	[132]
		Leaf nitrogen concentration (R2 = 0.18–0.86)	[132]
		Nitrogen fertilization	[133]
		Grain yield (R2 = 0.04–0.88)	[132]
Coordinates of the L*a*b* model	${\mathrm{L}}^{\mathrm{*}}$	Total chlorophyll content (R2 = 0.66–0.68)	[37,92]
		Chlorophyll a (R2 = 0.66) Chlorophyll b (R2 = 0.61) Carotenoids (R2 = 0.66)	[37]
		SPAD (R2 = 0.58–0.85)	[83,92]
	${\mathrm{a}}^{\mathrm{*}}$	Total chlorophyll content (R2 = 0.38–0.39)	[37,92]
		Chlorophyll a (R2 = 0.38) Chlorophyll b (R2 = 0.38) Carotenoids (R2 = 0.37)	[37]
		SPAD (R2 = 0.44)	[92]
		N, P, Mg, and Fe deficit	[7]
	${\mathrm{b}}^{\mathrm{*}}$	Total chlorophyll content (R2 = 0.62–0.81)	[37,92]
		Chlorophyll a (R2 = 0.81) Chlorophyll b (R2 = 0.74) Carotenoids (R2 = 0.81)	[37]
		SPAD (R2 = 0.31–0.81)	[83,92,134]
		Leaf nitrogen concentration (R2 = 0.58–0.86)	[134]
		Nitrogen fertilization	[135]
		Plant nitrogen concentration (R2 = 0.66–0.67)	[7,136]
Ratio of b* to a*	$\frac{{\mathrm{b}}^{\mathrm{*}}}{{\mathrm{a}}^{\mathrm{*}}}$	SPAD (R2 = 0.02–0.67)	[83,134]

R² is the determination coefficient for the regression describing the relation between the color parameter and plant characteristic. These coefficients are directly provided in cited works or are calculated as squares of Pearson correlation coefficients (R² for the linear regression). If several R²s are shown in the cited works (e.g., under different measuring conditions), the ranging R² is included in this table. The determination coefficient is absent from this table if the relations between color parameters and plant characteristics are not investigated or if the Spearmen correlation coefficient is analyzed in cited works. Relations with minimum R² ≥ 0.7 (for separate determination coefficients or their ranges) are marked by bold. Relations with maximum R² ≥ 0.7 (for ranges of determination coefficients) are marked by bold and italics. Relations with maximum R² < 0.36 are not included in this table because R² = 0.36 approximately corresponds with the correlation coefficient with absolute value equaling to 0.6, i.e., R² < 0.36 corresponds with the weak correlation. Non-marked relations are moderate and can be potentially used to further develop effective tools for estimation of plant characteristics (e.g., through the combination of several color parameters that have these relations).