I find I recolor stamps quite a lot. In Photoshop, there is a way to select a transparent image by clicking + Ctrl on the layer menu, and it will select the entire area of the transparent image.

This would be extremely helpful to select the entire area of a stamp when using the shape tool so that you can apply a color or texture to that area.

Even if I need to then go in and remove certain areas to give them another color, this would eliminate the bulk of my work and make it a little easier to apply textures and colors over existing stamps.