My son and I were wondering if we had a white cat, how could we (if we could) get it dyed safely.
Hmm… I would think that human hair dye would work well enough, but I am unsure is there are other effects of the entire body being covered.
Safe for you, or for the cat?
I’d recommend taking a picture of the cat, and colorizing it in Photoshop.
Um, I know some folks who used food colouring on their dog for Hallowe’en, but be advised it gets everywhere and the cat would lick it until his tongue was Technicolour.
It was the most harmless and non-toxic thing they could find and the Yorky went back to normal after a few weeks.
Well, I don’t think you could…unless you don’t mind losing the skin on your arms.
Lots of tips
Whilst some people chew their hair, most don’t lick it. Perhaps places that groom dogs & cats do something like that too. I’ll tell ya one thing, you aren’t getting a cat from me anytime soon. 
Let’s try it again and see if vB chops my post up a second time Lots of tips on cat dying here: Why Paint Cats; pictures too.
The book “Why Paint Cats, the ethics of feline aesthetics” likely goes in to more detail.
Dip it in molten bronze.
Same authors as “Why cats paint” - which is (as far as I know) a brilliant and subtle spoof.
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Kool-aide