While we're at it, a way of doing colour replacements either at transclusion time, or permanently, would be really handy for certain maps created by people with, um, dubious colour preferences :) Here's an example: http://en.wikipedia.org/wiki/List_of_European_Union_member_states_by_politic...
Strangely, there doesn't seem to have been any unified colour set adopted across English Wikipedia, but if one day such a thing was adopted, it would be handy to be able to transclude maps from Commons, respecting the colour preferences of each Wikipedia.
It would be a bit chunky for a [[Image:...]] command, but could technically be done that way: [[Image:foo.jpg|substcol:128,255,128:0,128,0|substcol:255,255,255:128,0,255]].
Steve