I'm a little confused about the approach to the frequencies here. Most light that we see (apart from laser light or the result of separating or filtering light with optical equipment) is not pure monochromatic light at a single frequency. This is clearly true for many colors in this chart which are given as combinations of additive primary colors. So, it is misleading to say that these colors have a single frequency or wavelength. Is the frequency given in the chart just the pure color that would be closest to the indicated color in some color space metric?