Change the colour of a specififc material?

I've read endless amounts of answers already pertaining to this topic, but none of them seemed to work correctly.

Basically, what I want to do is change the colour of two out of three materials on an object (But to different colours) and I can't seem to get it to work properly. This is what I've tried:

 foreach (Material matt in helmet.renderer.materials) {
                     if (matt.name == "Helmet") {
                         matt.color = Color.red;
                         matt.SetFloat("_Shininess", 0.2f);
                     }    
                     else if (matt.name == "HelmetTop")
                         matt.color = new Color (pc.EquippedHelmet.BrushColour.R, pc.EquippedHelmet.BrushColour.G, pc.EquippedHelmet.BrushColour.B);
                 }
             }

When I play the game and look in the inspector, I can see it created a new instance of each material than I can change through the inspector, which works, but I want the code to change the colour of the two materials...

Thanks