Pure spectral colors

The visible spectrum with approximate wavelengths.

The human visual system does not interpret all wavelength distributions in the same way. As a first approximation a full color image can be reproduced with three emission colors, red-green-blue ... or ... with the three secondary colors yellow-cyan-magenta but the situation is complex. Edwin Land was able to show that a full color image can be recreated with just two carefully chosen colors. ie any specral color can be mimicked with two other wavelengths.

An additional puzzle has intrigued the editor for many years. It is not possible to be certain that different people experience color in the same way. It is only possible to ascertain that they agree that two colors are different and the names they assign to the colors are consistent.