Why 3 colors?

There are 3 primary colors;
{yellow,blue,red}
And there are 2 intensity limits;
{black,white}
Perception of color shifts to white in high intensity, to black in low intensity.
3/2 symmetry of color reflects the quark/gluon and space symmetry.
Space has 3 dimensions, each dimension with forward/backward duality.
Quark/gluon symmetry determines the space symmetry,
and space symmetry determines the symmetry of color perception.

Color perception would evolve from intensity (black and white) perception.
With humans, color perception has a full octave spectrum.
Unlike sound, color has only one cycle, infra-red to ultra-violet.
But within one cycle, sound also reflects color.
{C,D,E,F,G,A,B}
can be compared to white and 3 colors;
{White,Yellow,Orange,Red,Purple,Blue,Green}
Black would be silence.
Tree top living would enforce a 3D phase (state) space in the mind.
Moving around in a 3D grid requires an inner simulation of this grid for fast response.
Essentially it is about 3D pattern recognition.
Color identification of each space locality is the result of this inner mapping.
Like the RAM (Random Access Memory) address in computers,
color is a fast indexing mechanism to label space.