yellow | yellow- green |
green | cyan | blue | violet | purple | magenta | red | red-orange | orange | orange- yellow |
FF0 | 8F0 | 0F0 | 0FF | 00F | 80F | F0F | F08 | F00 | F40 | F80 | FC0 |
000F | 0F00 | 0FF0 | 00F0 | F000 | |||||||
FF0 | 0F0 | 00F | F00 | ||||||||
0F00 | 000F | 00FF | 00F0 | F000 | |||||||
0F0 | 000 | 00F | F00 |
The primary colors that the brain (not the retina) perceives are
- yellow
- red
- blue
combining these gives the secondary colors
- orange
- purple
- green
One can see that these colors are intermediate between the primary colors
One would assume then that combining a primary color and a secondary color would result in a color intermediate between the primary and the secondary. And indeed most do. Except for cyan.
Cyan is not intermediate between blue and green. It is clearly a combination of blue and something. But what that something is is not clear.
I suggest that there were originally four primary colors. Cyan is between blue and the fourth primary color which no longer exists.
Retina
The original four color receptors were
- yellow
- green
- red
- blue
Except we didnt perceive the green receptor as green. We perceived it as a fourth primary color that no longer exists
Eventually we started perceiving the output of the green receptor as between yellow and blue. So we no longer needed four light receptors in the retina. So we dropped one. But instead of dropping the green receptor we dropped the yellow receptor.
Origin of the colors
Yellow, red, and blue are colorized, beautified versions of white, grey, and black. It isnt clear what the fourth primary color corresponded to.
white | yellow |
grey | red |
black | blue |