Table 1. Colour distance in a Maxwell colour triangle for ‘colour’ stimuli that are only learnt by free flying honeybees that experience differential conditioning.

Study	Stimulus pair	Triangle colour distance
Giurfa 2004 [20]	HKS 37N vs 43N	0.089
Avarguès-Weber et. al 2010 [21]	HKS 43N vs 47N	0.071
Avarguès-Weber et. al 2010 [21]	HKS3N vs 68N	0.084
Dyer & Murphy 2009 [22]	Similar ‘blues’	0.043
Current	414 vs 424 nm	0.039

The stimuli used in the current study are more perceptually similar than previous studies.