Jason Bradwell's 365/366 Photo a Day Blog

Red, yellow, and blue are the historical set of subtractive primary colors, mainly used in art and art education, particularly painting. It predates modern scientific color theory, which realizes that you can't really mix every color in the rainbow from these three. Which is why modern printing is composed of cyan, magenta, yellow (and black) to get a much wider color gamut.

Before the color names cyan and magenta were in common use, these primaries were often known as blue-green and purple, or in some circles as blue and red, respectively, and their exact color has changed over time with access to new pigments and technologies. T-Mobile is recently trying to trademark the color magenta, WTF!?

Mixing yellow and cyan produces green colors; mixing yellow with magenta produces reds, and mixing magenta with cyan produces blues. In theory, mixing equal amounts of all three pigments should produce grey, resulting in black when all three are applied in sufficient density, but in practice they tend to produce muddy brown colors. For this reason, and to save ink and decrease drying times, a fourth pigment, black, is often used in addition to cyan, magenta, and yellow.

The resulting model is the so-called CMYK color model. The abbreviation stands for cyan, magenta, yellow, and key—black is referred to as the key color, a shorthand for the key printing plate that impressed the artistic detail of an image, usually in black ink.