Table 1.

Colorimetric coordinates of the white, red and black plates used in the study

	L	a	b	c	H
White	88.88	−1.37	−2.44	2.79	240.73
Red	47.76	0.28	−1.46	1.49	280.99
Black	30.50	45.94	25.83	52.7	29.35

L: The L dimension of the space is roughly proportional to log-luminance and captures perceived changes along the black–white achromatic colour continuum. a, b: The a and b dimensions define a chromatic plane with axes corresponding to the red–green and blue–yellow opponent continua. c: Chroma is the perceived strength of a surface colour and the degree of visual difference from a neutral grey of the same lightness. H: Hue is the attribute of appearance that is often colloquially called colour