Well, I do tend to stick to few colors, usually black, blue and red. But that's when I want to be "austere" (most of the time).
OTOH, when I want to be "fancy", I like to mix colors: as in medioeval manuscrips, I like to use a color for capitals, enhance words or sentences with color (green, red), or passages (blue, black, sepia/browns), and illustrate here and there (capitals, drawings, mixing colors).
As a rule, I prefer to err on the austere side; yet, I can't but realize that a series of poems looks better with color combinations and drawings than merely using black all the time. Think, for instance of "The Hunting of the Snark", "Le Petit Prince" or "10 poemas de amor y una canción desesperada": yeah, they'll look nice in black, but wouldn't color add another dimension?
Hence the question.