Variegation is the process of making something more diverse, especially in its coloration. The variegation in a plant's leaves can give them a striped or spotted appearance.
One long musical note can be made into an interesting tune with some variegation in its pitch and tone. And adding variegation to the color of the ocean in your painting can lend it a more realistic appearance. This noun is often used by botanists (plant scientists) to describe the color variation in blossoms and leaves. The Latin root of variegation is varius, "spotted" or "varying."