Image effect or shader that renders alpha?

Is there a shader or image effect that can render a texture's alpha as color similar to the view mode? I'm working on a sort of FLIR type camera and currently using the Grayscale and Glow effects together with the "heat" value of each object stored in its texture's alpha.

Glow works pretty well, but it looks wonky if the object's regular texture is too dark and it washes out most of the general shapes.

I'd prefer an image effect though so I can just toggle it. I'll post some screenshots when I get back to my own computer.