Beard and Moustache Help

[Pseudosneeze]

During my sophomore year in college, I got a part in a play, Medea where I was playing an elderly Tutor. I was already using Panoxyl face wash for acne, and used it to make my beard look grayer for the part. Unfortunately, I don't think my facial hair has ever fully recovered from that bleaching. It's so much lighter than the rest of the hair on my chin and sides of my face. It's been a few years now, and had no idea it would last this long. Is there any way to fix this? Any input would be appreciated.