When you have multiple paint layers for a mesh, you can quickly view the paint from a single layer by soloing that layer in the Paint Layers window. The Solo options let you quickly toggle the visibility of all other layers on and off. You can also choose to display the solo paint layer as diffuse color, making it even easier to edit specific layer channels such as Opacity, Specular, and Bump.
To solo a paint layer
Only paint from the selected layer displays on your model, and paint from all other layers is temporarily hidden. The Visibility icon for the soloed layer displays in yellow, and Visibility for all other layers is turned off.
To solo a paint layer and display with diffuse color
Only paint from the selected layer displays on your model, with paint displaying as diffuse color.
To unsolo a paint layer
Paint from all visible layers displays on your model again.