a
: a phenomenon of light (such as red, brown, pink, or gray) or visual perception that enables one to differentiate otherwise identical objects
b
(1)
: the aspect of the appearance of objects and light sources that may be described in terms of hue, lightness, and saturation (see SATURATION sense 4) for objects and hue, brightness, and saturation for light sources
For pink light to be perceived, it needs red cones to fully react, and both green and blue cones to only partially activate.
https://gizmodo.com/if-the-color-pink-doesnt-scientifically-exist-why-can-1464266788
The definition of color from Merriam/Webster.
a : a phenomenon of light (such as red, brown, pink, or gray) or visual perception that enables one to differentiate otherwise identical objects b (1) : the aspect of the appearance of objects and light sources that may be described in terms of hue, lightness, and saturation (see SATURATION sense 4) for objects and hue, brightness, and saturation for light sources