Red represents low-energy X-rays, the medium range is green, and the most energetic ones are colored blue. The blue hand-like structure was created by energy emanating from the nebula around they dying star PSR B1509-58. The red areas are from a neighboring gas cloud called RCW 89.
Subliterate Cinephile does the math, and finds the corresponding panel from, I believe, CRISIS ON INFINITE EARTHS. Although the post blames Grant Morrison — just because it’s funnier — he actually didn’t come up with this one…it was Wolfman/Perez.
(Thanks to DWF and Franklin for emailing the link.)