My understanding is that the area just to the east of Brittany, including the city of Nantes, is one of the most conservative regions of France. That’s where the counter-revolution erupted in 1794. That part is blue as well. I don’t know about Brittany itself.
While the Red-State/Blue-State reference is funny, French politics is quite different from American. One big difference is the way France’s politicians react to events like this. A decisive vote one way in the U.S. would lead the losing party to do plenty of soul-searching and speeches about how it heard the voters. (Yes, even many Democrats did this in November.)
Chirac’s speech, however, was incredible, basically telling his citizens (1) you have ruined France’s position in the EU; (2) we politicians going to continue to work to pass the constitution anyway. Others in Paris and Brussels loudly proclaimed that the constitution will still be ratified, and trumpeted the fact that 9 countries representing 49% of EU citizens approved it. They forgot to mention that only one of the nine (Spain) approved it by referendum.
Say what you want about U.S. politicians, but they do listen to the voters much more than European leaders do.
-Illini