There exist questions for which there is no safe answer. This is one of them.
Shoe polish contains strong leather dye components. I once got a lot of black Kiwi polish on my hands in polishing a bunch of shoes and boots. They were so messy I did not bother wiping the polish off till I was done an hour or so later, and my hands were quite stained even after several handwashings and rubbing with isopropyl alcohol. The colorant was in the skin at that point.
Took about a week for all traces to vanish.
How well did the dye work since the cover is already colored?
Isn’t it a waste of the aniline dye?
It’s gorgeous. I started with the light tan iPad “Smart Cover”, and used this. The result is a rich, dark purple, no muddiness from the light brown at all. Even the brush strokes are pretty much invisible now that it’s dried. Better than I expected (I’d been prepared to toss it if it didn’t work). If I’d started with the white cover, I presume it would have been a little lighter. My primary motivation was to replace the tan, since everyone that saw the tan cover thought it was cardboard.
I got a couple of those foam “gesso” brushes from an art store to do the application with, since the dye comes with basically an oversize Q-tip, which would take forever.
On a related note, paste food dye works really, really well when you want to dye the cat.
We have a lot of fun at Easter in our house.
TimeWinder
This poster has been graped by the Grapist!
Quit making light of grape, grapists, and grape month.
I recently came across a youtube video (can’t link to it at work) where the person comes to the same conclusion (“human skin is basically leather”) and suggests you use your arm to strop the blades on your disposible shaving cartridge. I have been doing this ever since and it will extend the life of those blades greatly. There are actually better ways to strop the blades, but none are so convenient as simply using your arm.
IIRC, WhyNot knows. 
According to Johnny Quest, it takes at least 3 weeks.
I suggest you reconsider becoming The Purple Menace, or at least the Grape Ape.