Given how tough it is supposed to be, I am surprised you can see wood through it. Ebanol is cellulose and black phenolic resins, I don't think you can repair such a thing. You can certainly have it redressed, but that will only make the ebanol thinner.
Its basically thin layers of black paper that are making it black and it can be grey sometimes (in places). It is possible that redressing will remove the lighter makes and expose the next layer of black paper. But given its properties, it inst something you can blacken retrospectively, the material is too dense to absorb anything, surely?