Rainbows are comprised
of different wave lengths
of white light....
Sarcasm where required...
White light is somewhat analogous to white noise, in that it’s all perceivable (with our senses) frequencies at once.
Perceiving different wavelengths of light as colors is a quirk of the specialized brain cells in our retinas, and the firmware in our brains which processes vision.
If we ever openly encounter an intelligent alien species, they might well have a completely different method of perceiving photons and processing imagery which doesn’t discriminate wavelengths, therefore no colors.
[[Rainbows are comprised
of different wave lengths
of white light....]]
Well they seem to be afraid of the light and want to live in total darkness .