CMY color model
The CMY color model is a subtractive color model in which cyan, magenta and yellow pigments or dyes are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three subtractive primary colors: cyan, magenta, and yellow.
The CMY color model itself does not define what is meant by cyan, magenta and yellow colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the cyan, magenta, and yellow primaries are defined, the color model then becomes an absolute color space.
The CMY color model is subtractive in the sense that mixtures of dyes subtract specific wavelengths from the spectral power distribution of the illuminating light which is scattered back into the viewer's eye and is perceived as colored. Mixing of dyes is used to reproduce a gamut of colors, the resultant color from this layer is predicted by multiplying (not subtracting) the absorbance profiles of the dyes. This is essentially opposite to the additive color model, particularly the RGB color model, that applies to lights whose color depends directly on the light.
When the intensities for all the components are the same, the result is a shade of gray, lighter, or darker depending on the intensity. When the intensities are different, the result is a colorized hue, more or less saturated depending on the difference of the strongest and weakest of the intensities of the primary colors employed.
When one of the components has the strongest intensity, the color is a hue near this primary color (cyan-ish, magenta-ish, or yellow-ish), and when two components have the same strongest intensity, then the color is a hue of a secondary color (a shade of red, green or blue). A secondary color is formed by the sum of two primary colors of equal intensity: red is magenta+yellow, green is yellow+cyan, and blue is cyan+magenta. Mixing secondary colors will result in the dark versions of their common primary color: green+blue is dark cyan or teal, blue+red is dark magenta or purple, and red+green is dark yellow or olive. Every secondary color is the complement of one primary color: red complements cyan, green complements magenta, and blue complements yellow. When a primary and its complementary secondary color are added together, the resulting color would be the very dark version of the mixed primary color: cyan+red results into very dark cyan or dark teal, magenta+green results into very dark magenta or dark purple, and yellow+blue results into very dark yellow or dark olive. When all the primary colors are mixed in equal intensities, the result is black.
CMYK color model
CMYK color model is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself, that is used in the layering technique by printers to create different colors on a white paper. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key. It uses K, black ink, since C, M, and Y inks are translucent and will only produce a gray color when laid on top of each other.
- Levoy, March. "Additive versus subtractive color mixing - cs178 notes". graphics.stanford.edu. Retrieved 28 June 2019.