I've wanted to do a watercolor look for a long time, and when I discovered how easy it is to do, I had to try. This is simply H&M Whiteout as a base, with H&M Kingfisher on top. The blue has been applied together with nail polish remover to dilute it, and applied with a small brush.
More nail polish remover makes for a more sheer look, so you can layer it just as you want. I recommend putting top coat over your base color, to avoid the nail polish remover melting into the base color.