I'm not quite sure how this would work; the color models I have currently are three-dimensional so can be specified by three pieces of information (square x, sq

I'm not quite sure how this would work; the color models I have currently are three-dimensional so can be specified by three pieces of information (square x, square y, bar y). CMYK is 4-dimensional so you'd need something like 2 squares to specify a color. (Note that Photoshop's color picker doesn't have bubbles next to CMYK.)