Chances are that he will not darken too much. His coloring should stay about the same. Pastels are genetically brightens yellows and fades blacks. Usually having yellow eyes. Even if they do darken just a little because of the genetics there is no wa...
Let an art expert first check out that *provenance*, especially if it's a late Dali work, from 1982 to 1989. Many late Dali works are fakes, or works by Dali assistants who let Dali sign them at the end of his life.
Drawings Main (all links) drawings, watercolors, oil on canvas and analysis.