How about using make-up for people who have rosacea or dark pigmentation on light skin. That would, I imagine, have good coverage. You could also try 2 or even 3 shades lighter than your usual foundation. Ask in a large department store for samples to try at home. Superdrug have samples on display of all the less expensive major brands. Go in and try them to see what suits your skin so that the colour blends with the rest of your leg. Good luck.