RGB color is a model used for on-screen purposes, like digital and web-based graphics. In this model, red, green, and blue light are combined in various ways to reproduce a wide range of colors on the light spectrum. The RGB model is a light additive color model; colors begin as black and get lighter and lighter as more color (light) is added. This means that colors are added together to create lighter colors: in the summation of all light on the RGB spectrum, you generate white (#ffffff), and in the absence of light on the RGB spectrum, you generate black (#000000).
CMYK, also known as “process color” or “four-color,” is a color model used for printing purposes. The acronym stands for the four ink colors used for its printing process: Cyan, Magenta, Yellow, and Key (better known as black). The CMYK model is a subtractive color model; colors begin as white and then get darker as more colors are combined. CMYK has to do with ink – in the absence of ink on the CMYK spectrum, you generate white. And in the summation of all ink on the CMYK spectrum, you generate black. That’s right, the opposite of RGB!