Can I safely use food coloring or pet fur dye to differentiate my identical twin kittens?

Don't you dare put any sort of dye on them. You could give them different coloured collars. But if you really love them you will notice heir differences as others have said.

They are not identical. However, if you know of a product called "pet fur dye" then you answered your own question.

Those are not identical. They have different facial markings and coat patterns.

They aren't identical !!

You're going to be in trouble if you have identical twins yourself - aren't you??

Most cats will come when called. Why don’t you just call one and see what happens. I also agree with one of the previous answers, they aren’t identical, so maybe just get used to the different stripes each has on their face. As well I’m sure they each have their own individual personality, that should help you to tell them apart as well. 

I’m not a big proponent of collars on animals. I’ve seen too many get cats get stuck on stuff and some have even died while the owner wasn’t home. So I wouldn’t recommend collars. A dab on one ear if you still can’t differentiate would be fine. 

They're not identical.  Look at the 'M' on the forehead.  One has taller 'humps' to the M.  The other's are shorter, with the stripes coming together sooner.  And seems darker from the picture.   Plus the taller humped M cat seems to have a more angular face.  

You could try different color COLLARS.

Food coloring is fine. Cat safe dye is fine. I would keep it to a small area to make it easy to wash so you don't stress them out too much. Breakaway collars will work too. I used to use colored sharpies on mice tails to tell them apart. I would assume it would be fine for cats too. Put dots in their ears. 

A tab of color will do.

Lovely cats. You should buy cat collars for them with identity tags.

Yes you can I often do that with my hens and chickens I paint them with different colors