>About colors being assigned to parties, I distinctly remember an electoral map in TIME magazine just after the 2000 election that had Bush's states in red and Gore's in blue. I think it's pretty arbitrary.

I hadn't realised that.

Here the parties are very clearly colour coded:

Labour - red, although the reg flag logo was replaced with a red rose a few years ago to be less "challenging", they do still sing the red flag at the end of the annual conference
Conservative & Ulster Unionists - blue (with a hint of Union Jack) Mrs Thatcher must have spend thousands on a myriad of different colours of blue suits in her time.
Liberal/ Lib Dem - Gold/Yellow (but never orange) MPs tend to have a large wardrobe of gold ties and scarves.
Green Party - green, not surprisingly but see this article for a (lengthy} discussion on shades of green - red green, blue green and deep green http://www.earthscan.co.uk/samplechapters/1853837598Chapter1.htm

In Northern Ireland the colours green and orange mark the sectarian divide.

Maybe Rhuby can tell us how far back the colours go. What colour were the Whiggs?