Bizi,
My guess is that mostly they are not coloring them.
They are using high quality cameras.
Here is the explanation of this picture:
Quote:
Intense ultraviolet light from the hot central star ionizes atoms in the gas. In the picture, the
blue color in the center is ionized helium, the
cyan color of the inner ring is the glow of hydrogen and oxygen, and the
reddish color of the outer ring is from nitrogen and sulfur.
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Mari