The Pacman nebula in SHO. SHO means Sulphur, Hydrogen-Alpha, Oxygen and means the lines of these Molecules in the spectrum.
For each of these lines you have a filter which lets only pass one color.
When creating the picture, the three resulting images are combined where sulphur is set to red, Hydrogen-Alpha is set to green and Oxygen to Blue. Because of this combination you have a false color look.