I would wash it first to remove any mold and dirt. Then I would spread a coating on it - matching the original coating. Mobile homes normally have a snow white roof coating that could be used.
Do you know the brand and where you can purchase it?
I would wash it, sand it, n rinse well, let dry thoroughly... then use flex seal spray .. couple coats .. or rustolium spray couple coats!!
Here is some info on the how-to's as well as some products to consider: