To create this effect, you need a wet piece of fabric, a plastic garbage bag, acrylic paint and a brush. You pounce the diluted acrylic paint with the brush onto the fabric. I prefer to place the wet fabric into the garbage bag before I do this, so that I do not have to lift the wet fabric into the bag. That is be a bit messy to do :-). On this fabric I used blue and green acrylic paint. No particular brand as any brand will do. For this I used the $0,50 cent bottles from JoAnn.
After this the fabric bag was partly closed and left into a warm place for 3-4 days. Because of the way that the fabric is crunched the diluted paint creeps up a bit and you get this kind of effect: