Many, many yards use simple green to clean EVERYTHING...my first set of 300m seats, (not pro-am) where cleaned using simple green...and i freaked out about it to the guy. He says they have never had a problem with them.
It took me quite a while with leatherique/lexol to remove all of the stuff out of the leather. The black color really doens't tend to fade, but the white area, turns a nice brownish color to it after a while in the sun. Whoever gets those will have to just restore the heck out of them to remove the simple green stuff, if its not too late.
--Gorm