This year marks the 80th anniversary of the publication of the CIE 1931 Standard Observer for color measurement and specification. This is the basic standard that makes possible the plots you see of primary color triangles on the background of the "horseshoe" shaped spectral locus. It lead to the scientific design of color reproduction systems, derivative plots that indicate color gamut and reproduction accuracy, matrix calculations to improve the color rendition of color TV cameras and digital still cameras, and so on.
http://en.wikipedia.org/wiki/CIE_1931_color_space