People ask if these images are “real” and there are two answers for that. First is yes, these are real. A rainbow is real even though nobody else can see the rainbow you see. The dark side of the moon is real even though you can’t see it. Microbes are real even though they’re too small to see.
These nebulae are real, but the better question might be to ask what the colors signify. In these examples they are carefully chosen colors to map the different gases that are abundant throughout the universe. Hydrogen, the most common element in the universe is shown in green, oxygen in blue and sulfur is red. Knowing that you can appreciate how the gases are distributed.
And of course another reason for the color choices is to create an appealing work of art. If a rock or tree can be the subject of a fine art image then a nebula can too. Scientific images can also be art.
