Removed the EBC Ultimax rear pads this past weekend. The pads look 100% normal and are evenly worn. The rotors are also even across the surface confirmed by feel and micrometer. I am going to guess that the outer part of the rotor was heated to a higher temp and is discolled differently than the inner part. The entire inside surface of both of the rear rotors matched the color of the outer edge of the outside surface.