Electoral College election-result maps now nearly always show Democrats as blue and Republicans as red.
There have been many explanations as to why, but here are four new (?) theories:
1. Democrats are feeling blue (i.e. depressed) over the many years worth of election results that appear to be trending against them on a national level.
2. The human eye sees blue in the background and red in the foreground (yet another proxy metaphor for Democrats "falling behind") - the USAToday electoral college election-results map shows this very vividly - the red/blue contrast makes the map appear to be in 3-d:
3. All of the blue states (with just one exception) border major cold water lakes or oceans. Water and cold are both usually represented by blue. The county-by-county electoral college map of the 2004 USA Presidential elections shows a sea (pun not intended!) of red counties with blue speckling - and nearly all of that blue tends to be near a major water source (river, lake, or ocean):
4. As per the map at John Kerry 2004: The Unofficial Kerry for President Blog (which was originally from The Washington Monthly and Calpundit: The Red and the Blue), it appears that many of "the blue states are the states which pay more to the federal government in taxes while the red states receive more government money than they pay in." Since in accounting "in the red" means in deficit, that would also clarify the color choices a bit...
And a quick note to acknowledge the double irony that in the rest of the world Left / Liberal / Socialist / Communist parties are Red, and during the American Civil War, the North (Republicans) were Blue (i.e. "the Blue and the Gray")
Finally, it is agreed that all this Red vs. Blue stuff is unnecessarily divisive. This post was just meant to have some fun with the choices of colors, not that fact that discourse has been reduced to them. Be sure to see Boing Boing: Purple Haze for a more nuanced view: