grayscale
Channel (digital image)
List of monochrome and RGB color formats Monochrome palettes section
List of software palettes Color gradient palettes and false color palettes sections
Achromatopsia, total color blindness, in which vision is limited to a grayscale

image grayscale
define grayscale
wikipedia grayscale
weblio grayscale
kotobank grayscale
jisho grayscale