I've noticed for a long time that in a color wheel, Cyan Magenta and Yellow are much brighter than Blue Red and Green. A couple of years ago it finally dawned

I've noticed for a long time that in a color wheel, Cyan Magenta and Yellow are much brighter than Blue Red and Green. A couple of years ago it finally dawned on me why that was - the way our monitors are designed, Cyan Magenta and Yellow are producing twice as many photons! They each produce full intensity on two primary colors instead of just one. They don't look fully twice as bright because of the eye's non-linear response, but it's definitely a noticeable effect.