Some vinyl graphics *can* discolor if:
a) the surrounding paint is not clearcoated, and the wax/polish deposits pigment into pores in the vinyl. (especially with light colored graphics on a dark car).
b) the vinyl has embedded dirt, that is unequally removed by unequal application of the polish/wax either chemically or abrasively depending on the type of cleaners in the wax.
c) a harsh cleaner is used that 'bleaches' the color out of the vinyl (also applies to mild cleaners on inferior grade vinyl with poor color fastness).
d) harsh abrasives have ever been used on the vinyl causing scratches that will trap dirt/pigment.
For the most part, it is OK to use a non-abrasive wax/polish on vinyl graphics without causing harm (other than the wax residue along the edges).
Just avoid harsh chemicals and abrasives, and stick with a pure wax/polish and you should come out 'looking good.' ;-)
Don M
'02 Cavalier LSSC
2200 DOHC