[GrantMoyer]

The wording on the article is correct, despite being confusing. The CIE 1931 RGB primaries each stimulate multiple types of cone in human eyes, so the RGB Color Matching Functions (CMFs) don't represent individual cone stimulations.

However, the CMFs for LMS space[1] do directly represent individual cone stimulations over. Like the CIE RGB CMFs, the LMS CMFs can also be thought of as the required intensities of three primariy colors required to reproduce the color of a given spectrum. The reason these two definitions coorespond for LMS space is that each primary would stimulate only one type of cone. However, unlike CIE RGB, no colors of light which stimulate only one type of cone physically exist.

Finally, CIE RGB and LMS space are linear transformations of each other, so the CIE RGB CMFs are linear combinations of the LMS CMFs, so each CIE RGB CMF can be though of as representing a specific linear combination of cone stimulations (the combination excited by the primary color).

I often find it easiest to reason about these color spaces in terms of LMS space, since it's the most physically straightforward.

[1]: https://en.m.wikipedia.org/wiki/LMS_color_space