Does the skull have blood stains? Why would you want to mix chemicals? I would say hell no!
Just put the skull in 30 volume and heat it. Watch the skull turn white in seconds.
Cause my well water is full of iron and makes skull orangish tint. Peroxide dont do squat to the iron. I dont soak my skulls in it for more then 20 minutes. I was just curious if long periods of time would harm them or not.