
Originally Posted by
Olaf the Unsure
The main reason I use purple myself is because of the contrast it provides with the other colors, giving the OE a unique color among the majors.
The other factor, for my tastes anyway, is that the darkest shades of any of darker colors (red, blue, green, etc.) look much too dark when the map is zoomed in. It's one thing to make a map that looks great when zoomed out, but gameplay often requires that you zoom in, and the darkest shades tend to obliterate the map details. Using purple allows a distinctive, contrasting color, without having to go to a too-dark shade of a more common color.
(I frankly hate the zoomed in version of the political map in any color. The real modding prize should go to whoever figures out how to make the zoomed out version of the political map work zoomed in.)