There are several remedies. Years ago I would always carry with me a Sharpie pen to basically "re-color" :biggrin: those trouble areas.
Luckily today there are advances that help us out with these problem areas. I now use a 2-step process which first cleans rubber and moldings of all dirt and wax residue and then if needed a dye which will restore the black color. Many times the dye step is not needed because the cleaner step works so darn well!