The Solid Color layer type, found within the Selected Layer box of the Texture Synthesis dialog, fills the layer with a solid color.
The controls for this layer type are organized into two sections. The Color section contains a single property defining the color to fill the layer with, while the Blend section contains the common controls described here.
One use of Solid Color layers is to fill in the gaps left by the layers above.
In this example, gaps between manually placed stones are filled with black.