This is why I make my customer faction's color pink. Pink looks the most distinct from everyone else.
That said, even the default factions sometimes have similar colors. It's hard to tell which border belongs to who sometimes. Fortunately they added in the feature to tell whose territory a square is on mouse-over, but I would like some way to not have to check like that, and instead just look and know. Someone had previously suggested having 2-color borders for everyone. That would work. Also, not increasing the brightness of the colors for the borders would help, as well. If both those were added, I wouldn't have to play pink anymore.
