Multi-color 3D printing sounds wonderfully simple until you actually watch the printer do it. You load a few spools, a**ign colors in the slicer, and expect the machine to produce something that looks a little more finished than the usual single-color part. Then the preview shows you another number sitting beside the model weight, and it’s not nearly as cute as the colored preview. The printed object might use 40 grams of filament, while the purge waste quietly asks for 70 more.