The Overview Effect
Blue and white. Some browns. Some green. Ever since humans could, seeing Earth from above was a source of awe. Perhaps what cathedrals had been scale models of.
Nowadays astronauts are trained not to look at it. In half of them it causes psychological distress before the mission is over. Back on the planet suicide is far from rare.
Don't look down, they are told. No matter how tempted.
Blue and white. Some browns.