What stars and composition of gases should my planets have to have a sky for each colour in the rainbow?

There are seven planets, and each one has a different coloured sky. One has red, one has orange, all the way up to indigo and violet. Of course, they don't have a sky this colour all the time, but preferably for most of the 'daytime'.

However, those aren't the only limitations. Humans must be able to survive in each of the seven without special equipment, and it must be possible for people from any one planet to be able to survive (maybe with a little special training) on any of the other planets.

These must be 'humans', with at least roughly identical anatomy to us on Earth, though the 'blue' planet doesn't have to be Earth.

The tilt, composition of the bulk of the planet, colour and kind of star, can be different if necessary, and these planets do not have to be in the same solar system.

What is the best way to achieve this?

posted over 6 years ago

Piomicron‭

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