Now that I think about it, there was some discussion about the primary colors of light being different than the primary colors of pigment, but, again, that was 20 years ago.
The difference is additive vs subtractive colors for emissive vs reflective sources of light respectively.
For emission sources such as stars, lamps and projectors, the primaries are RGB or red, green, blue.
For reflected light such as in print and paint, the primaries are CMYK or cyan, magenta, yellow and black.
Then you get into color space to describe the mix...