
Since time immemorial (or at least, since color televisions have been available), TVs have used 3 colors: red, green, and blue. Combinations of these three color building blocks produced the increasingly wide spectrum of colors you now see on the screen in front of you. Print, meanwhile, almost always uses 4 colors: cyan, magenta, yellow, and black. RGB is an additive color space, meaning the three colors combine to form white. CMYK is a subtractive color space, meaning the three main colors form black, or "K."
Sharp is working on incorporating cyan and yellow into the red-green-blue color set displays currently use. According to the company, this CYRGB color set can reproduce over 99% of visible surface colors (paints, pigments, and other colors that reflect, rather than emit, light).