When I was a kid I read a children's story (it was part of a short series) about a boy who travelled to another planet, possibly as a sidekick or travelling companion to someone else. The person who owned the spaceship had it painted with a futuristic paint that made it match its surroundings. The paint was given to him by aliens he had helped out prior.
In the story, they travel to a planet (possibly surrounded by crystal moons) with a large tower, and the boy needs to get in to the tower (which I believe was also a large crystal, or at least very large and bright) for some reason, possibly to retrieve an item or save someone. He was able to use the low gravity to get into the tower to do what he had to do.
The boy eventually had to escape the tower, and had troubles finding the spaceship, as it had changed colour to match the surroundings. He and the ship's owner eventually escaped.
A whole bunch of Googling suggested that it might be "The Sometimes Invisible Spaceship", but there's no photos or plot description available.
Does this story sound familiar to anyone?