The Blend commands create a series of intermediate colors from a group of three or more filled objects, based on the objects’ vertical or horizontal orientation, or on their stacking order. Blending does not affect strokes or unpainted objects.
To fill the intermediate objects with graduated blends between the frontmost and backmost filled objects, choose Edit > Edit Colors > Blend Front To Back.
To fill the intermediate objects with graduated blends between the leftmost and rightmost filled objects, choose Edit > Edit Colors > Blend Horizontally.
To fill the intermediate objects with graduated blends between the topmost and bottommost filled objects, choose Edit > Edit Colors > Blend Vertically.