I was thinking of a color panel similar to that in Universe Sandbox 1, however, this panel will edit individual components of a planet.
Ill see if I can image it here. Atmospheric light refraction (the sunset/sunrise) depends on the color. Eg. Red atmosphere= Blue sunset/sunrise. This feature might be a good idea to change the appearance of a planet until the advanced composition system is released (where composition affects color, currently there are not enough materials or specific elements/factors included in the game to properly do this).
COLOR---------------------
Atmosphere Color:
- <--- The sample color is shown in the square.
Ocean Color:
Surface Color:
Cloud Color:
Ice Color: (could be automatically selected from the Ocean Color)
Maybe a layered template system for things like surface color could be used. This stops the surface color being uniform throughout the planet. Each layer will have a different tint, though similar to the one selected. The layers could be ordered by altitude (color depends on altitude, this allows creation of realistic biomes), temperature (this is similar to altitude, because the higher the altitude, the lower the temperature) and so on. The amount of layers could be edited too, for more variation throughout the planet's surface.
A "Sand effect" feature could be added to create a realistic texture to planets, and remove the plain uniform color selected in the menu. I have attached an image of what this sand effect might look like.
A gas giant's color will be based on layers placed depending on altitude (there are several layers of cloud on a gas giant). This will enable the creation of quirky planets like Jool, the much loved green gas giant from Kerbal Space Program.
Here is an image of two blocks. The one on the left is without the sand effect, and the one on the right has the sand effect enabled. This screenshot is taken directly from The Powder Toy, but it shows what I am thinking about.