Ashen or ash-like skin color anywhere on the body may indicate a few different things. If by "ashen" you mean pale, this could indicate a low blood count, such as in anemia. Healthy blood flow lends a slight pinkish hue to the skin, and if this is lacking, the area may look pale, slightly greenish, or slightly grayish.
If the skin really looks like the color of "ash", a deeper more persistent gray or gray-blue color, this could potentially be due to a side effect of certain medications, with or without interaction from sunlight.
If the condition is persistent, I do recommend a visit to the doctor, because a noticeably ashen color may indicate something that is easily remedied and if not easily remedied, then still important to be evaluated.