RGB are the primary colors used in additive color mixing, CMYK are used as the primary colors for subtractive color mixing which is used in offset printing and similar processes.
In reality, artists often use different base colors anyway. One way to do it is to have 2 versions of the base colors, one warm, one cold. The reason is that for example a greenish blue like Cyan would make it harder to mix vivid violets (by adding a red on the other direction of the color wheel). So you use a greenish blue (Cyan) and a redish blue (e.g. Aquamarine), a blueish red (e.g. Magenta) and a yellow-ish red, and so on.
elcapitan|3 years ago