[Colour as we perceive it is a form of electromagnetic radiation between 400-790 teraherts. It's lower than infrared, microwaves, and radio; higher than x-rays and ultraviolet.]

[We don't see pure colours. They are spectrums that our visual system approximates, which results in our experiencing of the dominant color.]

[Colour constancy refers to the phenomenon of perceiving various shades of a colour as the same, despite there being subtle differences between them.]

[Human eyes have millions of photoreceptors called cones that can be divided into three sizes and each is more sensitive to a certain spectra: short (blue/violet), medium (green), and large (red/yellow-green))

[Ganglion cells antagonistically combine signals from the cones, which makes red compete with green, and blue compete with yellow.]

[There is no purple as pure and dominant. Ganglion cells perceive red and blue simultaneously.]

[Women rarely have colour blindness because they have two X chromosomes, which is where the genes for cones are located.]

[A dog may have a hard time finding a red ball in green grass because they are naturally are dichromatic, which means that one of the three cone types is nor present. This is common in mammals other than humans.]

[Some hues have wider perceptible ranges of saturation and lightness: the color space is not uniform.]

[Using a Lab color picker can result in more uniform lightness than HSB.]

[In the additive RGB color system used by screens: red and green combine to make yellow, red and blue to make magenta, and blue and green to make cyan.]

[Whereas RGB is an additive process the mixes towards white, CMYK starts with white and subtracts by reflecting light through pigments.)

[Color management between color profiles relies on Lab representation to produce colors that are ultimately not identical but metamerically the same.]