This image is L_HaRGB, where Ha:R (60:40) was used for the Red
channel, identifying ionized hydrogen (HII) star-forming regions in this
galaxy as they appeared 3 million years ago. If you "mouse-over"
the image, you will see it change from just LRGB (no mouse-over) to LHaRGB
(mouse-over), giving a better sense of where these HII regions are located.