A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components.
RGB – Media that transmit light (such as television) use additive color mixing with primary colors of red, green, and blue, each of which stimulates one of the three types of the eye’s color receptors with as little stimulation as possible of the other two. This is called “RGB” color space. Mixtures of light of these primary colors cover a large part of the human color space and thus produce a large part of human color experiences. This is why color television sets or color computer monitors need only produce mixtures of red, green and blue light.
CMYK – is possible to achieve a large range of colors seen by humans by combining cyan, magenta, and yellow transparent dyes/inks on a white substrate. These are the subtractive primary colors. Often a fourth ink, black, is added to improve reproduction of some dark colors. This is called “CMY” or “CMYK” color space.