Marking out in UV

I have an elaborate façade of a building.
Is there anyway to temporarily colour in the (say ) windows on the default screen so that when I come to re-work the UV after unwrapping it I can work on it in a paint package so that I know what or where the windows are.
And … any books that go into Blender with more depth than Blender for Dummies?

Create a material and apply that material to the faces that make up the windows, or just make them a separate object.

Thanks Richard, I’m still learning.