What does the planet's "atmosphere" color mean???

[The Bacon Chemist]

What does a planets "Atmosphere" color mean? I know there are 4 types of planets (Earth-Like, Ice Planet, Alien, Mars-Like) and I think light blue means Earth-Like and dark blue means Ice Planet, but what do the others mean?

 

[WeedLOL]

http://www.starmadewiki.com/wiki/Planets They just signify what kind of planets they are in the distance.