The characteristic color that is determined by its wavelength as red, green, blue, purple, yellow, etc., and excludes white, black, and shades of gray in reference to the visible spectrum of light.
See Alexandrite Tsarstone collectors guide, Definition of Hue, http://m.alexandrite.net/viewpage.html?id=GG-093-00005 (The characteristic color that is determined by its wavelength as red, green, blue, purple, yellow, etc., and excludes white, black, and shades of gray in reference to the visible spectrum of light.) (as of May. 21, 2026, 18:05 GMT).