Important point. I had already decided that Pyroiedes had red skies, and Eosphorus is always cloudy -- but that left some others. On a minute's reflection -- Tellus and Phaethon have blue skies, Phainos has violet -- and Stilbon -- Stilbon I will decide later. As I will about Selene. When relevant.
Though, technically it was not relevant at this point in the story. I just gave the man baby-blue eyes and tripped merrily on. It's a good thing I have a file where I note down details like that. Otherwise I would forgot by the time I actually have to refer to Phainos's sky color.
It's amazing the triviality of the details that can cause you realize you need to develop something more.