Currently your textures look like you have run a photoshop filter over them. How are you creating these textures? If you're aiming for a more realistic style, use photographs as blending layers or points of reference for painting in detail by hand. Edit: Look at the thread directly below this one, "10 texturing…
Colour and diffuse maps are the same thing (at least, when referring to them in game art terms). They should contain just as much detail as the other maps, it's just that they just all contain different information. The diffuse contains the colour information of the surface and usually there's at least a wee bit of implied…