A fun fact I learned recently, after years of casually skimming color science, is that our eyes cannot focus the entire visual spectrum at once.

That’s why our cone response to the spectrum looks like https://en.m.wikipedia.org/wiki/Cone_cell#/media/File%3ACone... instead of having cleanly segregated red vs. green responses. If it was segregated, we could only focus on red or green but not both. By having a heavy overlap, we can get a sharp focus on yellow. And, the visual system makes the full spectrum work by deriving the red vs. green concepts from the difference between the two cone responses. Blue focus is accepted as a necessary sacrifice.