Take some 240 grit wet/dry sandpaper and a flat sanding block, and wet-sand the discolored white rubber off the letters (only!). Don't sand or scrub the black rubber. Believe me, all white letters and whitewalls have this discoloration problem. But yes, the BFGs seem to be extremely bad. (Also, don't worry, you won't sand the white right off, it is very thick)
