For a bit more detail in that step at the retina, here are the relative responses of the different cones to various wavelengths (normalized to max = 1):<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Trichromacy#&#x2F;media&#x2F;File:Cones_SMJ2_E.svg" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Trichromacy#&#x2F;media&#x2F;File:Cones_...</a><p>Once you account for how much light comes off the object at each wavelength, these curves determine how strongly they impact your color perception. S&#x2F;M&#x2F;L stand for short, medium, and long, and are the names we give to the different cone types based on the relative length of waves that stimulate them.<p>As you can see, we don&#x27;t have a very balanced view of the &quot;visible spectrum.&quot; Butter, for example, is about 1.5x as reflective at 400nm as 450nm. But your eyes are something like 20x as sensitive to the light at 450nm (near peak sensitivity of short wavelength cones), so that light has a bigger impact on activating the short cones. 450nm is also picked up by medium and long cones, while 400 is pretty much below their range.