A three-dimensional printer uses transitional lengths of build material to facilitate changes from one color to another during a fabrication process, and more generally to achieve multi-color objects corresponding to color patterns on the surface of a three-dimensional model. The transitional lengths of build material may be positioned inside a fabricated object, such as for infill, or outside the fabricated object where undesirable aesthetic properties of the transitional lengths will not impact the desired distribution of colors on the surface of the fabricated object.