Yeah, I think the Alpha 16.1 update created some unintended changes. Every single planet I terraform gets blue clouds, I have not been able to get them any other color. As for the "stationary" clouds, I don't think they are, because if you fill the planet with water until the land is covered, it still retains a lighter color around the surface feature that was covered.
Or it could be terrain and not clouds. It depends on the random planet spawned. One almost looked like snow-capped mountains when I was spawning planets. You can report it with the in-game feedback, that's what I did.