you need to create new textures for diffuse, bump and spec, based on your colour channel. Try making a copy of it, desaturating it, and applying it to say diffuse. Test it out in maya, then start tweaking it in photoshop (brightness, contrast etc). Depending on what you are texturing this may be enough, or may not (for some wood textures for example I've gotten good results for diffuse, spec and bump this way pretty quickly).
I think the channels you are seeing are r, g and b channels.