https://www.cnet.com/news/hubble-hooks-a-crackin-crab-nebula-image-for-29th-anniversary/ > Some of the material from the red giant is pulled to the white dwarf, which in turn ejects it outward, feeding this spectacular nebula formation. "The bubbles of gas and dust appear brightest at the edges, giving the illusion of crab leg structures," NASA said. > Hubble gathered the images used in this composite view in March. The colors indicate the types of gases in the nebula: red is sulfur, green is hydrogen, orange is nitrogen and blue is oxygen.