CMY color model

CMY color model is a color model, used in color printing. CMY refers to the three inks used in printing: cyan, magenta, and yellow.
The CMY model is subtractive. It means that it "subtracts" or masks colors from white background of the paper. The ink reduces the reflected light. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.
White is the natural color of the paper, while (nearly) black is made by a full combination of colored inks. 
Unlike CMYK color model, it does not use additional black ink. So, it is not such economic and not so good at reproducing dark hues.