I eyeballed a couple of tablespoons' worth of each flavor in the muffin tin, then attempted to instruct my almost three-year-old on proper painting technique (in this case, it's recommended they first dip their paintbrush in water, then in the Kool-aid powder).
My kid tends to stick with one color at a time....and at the moment finger-painting is out. He doesn't mind getting messy, but he prefers paintbrushes right now. I painted with the other colors to see how they turned out.
After he saw that, there was no turning back.
He usually ends up messing with the water when he paints, so after awhile the colors got a little diluted. I did notice that the store-brand flavors (lemonade and grape) were less vibrant then. But the name-brand flavors (cherry and lemon-lime) stayed pretty bright. So it might be worth investing the 20 cents a packet for name-brand (as opposed to 12 cents for store-brand!).
So what's the verdict?
I think he likes it!
Pros: Cheap. Easy. Vibrant colors. Smells AMAZING.
Cons: Some colors dilute easily. Might stain skin and/or clothing (my kid didn't use his hands to paint, but did get some on his face. None of it got on his clothes from what I can see so can't make a call about how washable the Kool-aid is). Since it smells good, some kids might want to eat it (which isn't terrible, but you'd have to teach them that not all paint is edible!).
All in all, we both really liked this activity and will definitely do it again!