The brilliant and beautiful colors of a bubble are directly related the the thickness of the soap film surrounding it. When light shines on the soap film, some rays are reflected from the upper surface of the film, while others are refracted through the film and reflect off its lower surface. These reflected rays have different phase shifts and their interference is what causes the colors we observe. The color patterns themselves reveal the interior flow of the soap film, in which gravity tries to thin the film and surface tension tries to distribute the film evenly. (Photo credit: R. Kelly, A. Fish, D. Schwichtenberg, N. Travers, G. Seese)
The Colors of Soap
