Watercolor-eating Ants???

This is from Chris, who posted this to a list I'm on. Frankly, I'm baffled. Any guesses as to why the ants are doing this (other than 1. they could be having a Peter Max flashback, 2. it's mating season and they're getting all dolled up to get dates, or 3. they really do put sugar in everything!)

I came home tonight to find my box of Prang water colors covered in ants. I know water colors are held together with gum arabic, but I'm not sure what that's made of or if it's sweet. Any ideas on why the ants are eating my water colors? I don't think they're after the water since there's a shallow bowl of clean water sitting next to the paints.

The ants aren't on the outside of the paint box. They are in the wells of paint. They seem to like the aqua blue and copper best followed by orange and green. There are 30-40 in each of the wells - the sort of look like antelope around a watering hole. It's just cheap paint - I got it for .99 last fall before school started at Staples...