Here is some visual support for that explanation: https://en.wikipedia.org/wiki/Color_spaces_with_RGB_primaries https://en.wikipedia.org/wiki/Color_spaces_with_

Here is some visual support for that explanation: https://en.wikipedia.org/wiki/Color_spaces_with_RGB_primaries https://en.wikipedia.org/wiki/Color_spaces_with_RGB_primarie... It's fortunate that we mostly have 3 categories of cones and also 3 spatial dimensions. Notice that magenta is a vertex (of 8 vertices) in the cube, along with Yellow and Cyan too. How the particular space (of activation to the 3 categories of cones) is carved out by that cube is something we engineered, and in fact is different across different printing and display technologies.