The term "parti-color" refers to the pattern, design, or composition of an object or item that has two or more colors. The antonym of parti-color is "monochromatic," which means that something has only one color or shades of one color. Other antonyms for parti-color include "uniform," "homogeneous," and "monotone." These words describe an object or item that lacks the variety and contrast of parti-color. Another word that is the opposite of parti-color is "plain," which refers to something that is simple and lacks decoration, pattern, or color. Thus, depending upon the context, multiple words can be antonyms for "parti-color.