I had my old Belkin Vue Clear Grip case replaced to the newer revised case with bigger cutout for the camera flash, but what I have noticed with both cases is they start to discolour in the same areas. See photo below to see what I mean.
This is only really noticeable with my white iPhone 4, and not so on my black one.
Its not dirty either, as I have washed it, thinking it maybe dirt, but I feel it maybe caused from the heat from the iPhone 4?

This is only really noticeable with my white iPhone 4, and not so on my black one.
Its not dirty either, as I have washed it, thinking it maybe dirt, but I feel it maybe caused from the heat from the iPhone 4?