Showing a variety or a change of colors; multicolored.
Example:
The Wizard of Oz begins in black and white but suddenly becomes gloriously polychromatic once Dorothy and Toto land in Oz.
Male peacocks are almost miraculously polychromatic, with their feathers of gleaming blue, green, white, and brown. The polychromatic content of light becomes apparent when it passes through a prism like mist or a faceted piece of glass; the prism organizes it into its distinct wavelengths, each creating a band of color in the rainbow. Polychromatic takes it meaning straight from its roots: poly-, "many," and chrom-, "color."