UBCForce brings us another video featuring rainbow worlds and its music.
Rainbow worlds are planets which produce a “rainbow-like image” and have a large amount of valuable minerals. When a player discovers a rainbow world, the player can tell the Melnorme to receive 500 credits. There are 10 rainbow worlds located in the game, and if the points are joined together, they form a triangular shape where Groombridge is the tip of this triangle.
The player can find these worlds by chance or through character dialog who mention the strange things they find in space.
Thanks UBCForce for these videos.
More info: UQM Wiki