We have a new Masonite fiberglass entry door that was discolored by the chemical that the brick mason used to clean the brick. I think it is muratic acid. I was planning on staining it, what can be done to bring the whole door and sidelights back to one color.
Given the date on the picture, I am probably answering a little late.
I'll respond anyway. You should be able to buy a primer to closely resemble the original color. Ask the paint store guy to tint the primer and tell him you realize it will not be a perfect match for the chip. Prime the door and them follow the directions of the door manufacturer on finishing.