Fan Casting Alien Sky in Sort by Tropes

An unusual-looking sky is a surefire way of showing the audience that the characters are not on Earth, or at least not on Earth as we know it. Maybe there are two moons, or three. Perhaps Earth's all-too-familiar moon, the one in so many love songs, is broken into so many pieces it's become a ring of debris around the planet. The sky might be dominated by a huge gas giant, suggesting that you might not be on a planet at all (if you are, it must be very close), but instead a very large moon similar to Jupiter's Galilean moons. The sun is a different colour, or has a sibling visible in the sky alongside it. The daytime sky is a lovely shade of green, red, or deep purple. The stars are in strange shapes and colors, or move around at visible speeds — or perhaps the nighttime sky is empty. Maybe the sky is simply home to cloudforms that are not of this world... or lifeforms. Or rocks.