This is missing lume. No bleach is going to restore missing lume and even if it is moldy lume, you run the risk of the bleach eating away and decomposing the lume beneath, making the dial unusable. I have seen people also use a fine tooth brush in an effort to remove the top layer of the lume revealing the creamy color below. In my eyes, the lume is missing on this dial.
Will the OP please tell us if the lume is black from mold or missing completely?