Gradation in a multicolor surface refers to a continuous flow from one color to another in a way that no clear pattern is established, and the boundaries between colors are imperceptible, at least from a distance. The transition from one color to another should occur over a significant percentage of the surface in order to avoid the appearance of any rough geometric boundaries. Not every surface where colors bleed into each other is classified as a gradation; only those where large blocks of similar color appear together, and where the transition area is large. The gradation between different colors can occur in any direction or in multiple directions, and may be between similar shades or very different colors.

The transition occupies a substantial part of the surface. Small areas of bleeding between otherwise sharply bounded colors do not establish a gradation.

The transition can run in one direction or several and can join similar or contrasting colors. Its broad, gradual character distinguishes it from clearly bounded geometric patterns.