Redshift and blueshift factor in, too. Galaxies are all in motion. Some galaxies are coming towards us, some away from us, some at incredibly fast speeds. These relative motions compress or elongate the frequencies of the light coming from them, so they get pushed up the spectrum to red or down the spectrum to blue and violet, and everywhere in between.
Since this more or less applies to each given galaxy as a whole, for the most part, it would give lots of galaxies different apparent colors from our perspective on earth.
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