Which of the following is an example of extraspectral colour?
Another observation of basic impoance is the demonstration that the sensation of white, any spectral color, and even the extraspectral color, purple, can be produced by mixing various propoions of red light (wavelength 723-647 nm), green light (575-492 nm), and blue light (492-450 nm). Red, green, and blue are therefore called the primary colors. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 12.
Red
Green
Blue
Purple