" It is now almost possible to assign color combinations, based on the colors of clouds and sky, to every planet in the Solar System—from the sulfur-stained skies of Venus and the rusty skies of Mars to the aquamarine of Uranus and the hypnotic and unearthly blue of Neptune. Sacre-jaunt, sacre-rouge, sacre-vert. Perhaps they will one day adorn the flags of distant human outposts in the Solar System, in that time when the new frontiers are sweeping out from the Sun to the stars, and the explorers are surrounded by the endless black of space. Sacre-noir. "

― Carl Sagan , Pale Blue Dot: A Vision of the Human Future in Space