That, my cats do. Lol. Yeah, I’ve looked up all options for dyeing yarn & found that I only liked the food coloring & Kool Aid.
That’s the main reason I posted this thread, I wanted to see which of those 2 people prefer more.
Food coloring is an acid dye, which is what’s in Kool Aid and dyes for frosting.
Any dye you find in food is acid dye. Not all acid dye is food-grade, however. I recommend food-grade dyes because they’re safer to use.
All acid dyes require acid to set, and work better with heat. When I dye with acid dyes, I always heat on the stove.
Kool Aid has ascorbic acid (vitamin C) in it, but other dyes will need acid added. White vinegar is the easiest to find in a grocery store, but you can also get non-food-grade ascorbic acid from a store that sells dyes.
I promised something to someone who wanted purple, and I couldn’t find purple yarn, so I used 100% undyed merino wool and dyed it with grape Kool Aid. It turned out beautiful, but she wanted to know why it smelled like grapes. Three years later, it still smelled like grapes. She actually liked it, luckily.
I’ve used nothing but Kool-Aid for my yarn & every time it has come out amazingly!
I don’t see the point in messing around w/ acid dyes or any other type of dye when I can just mix up some Kool-Aid, soak my yarn in vinegar, paint my yarn with the Kool-Aid, cover in plastic wrap & then pop it in the microwave.
Plus, I just LOVE that my yarn smells like that specific Kool-Aid scent afterwards for quite some time, hehe. 
I like using acid dyes because I have a much wider range of colors, it is far, far more cost effective and I don’t like having my fibers smelling like fruit.
All food grade dyes are acid dyes. Not all acid dyes are food grade.
Kook Aid includes acid dye. It also includes ascorbic acid (vitamin C) to make the dye take. Food dyes have a much wider range of colors than Kool Aid (although Kool Aid has a wide range if you combine the right flabors), but don’t include acid and you have to add acid yourself, which most people do with vinegar.
Food dyes, including Kool Aid, are far less toxic than any other dyes available, which is why I use them.
They work well on protein fibers (wool, alpaca, etc.), silk and nylon.
Good luck!
Yeah, I must say I’m a Kool-Aid addict.