As I'm french, I know something about the subject. Typically we use the green, red and yellow. Gallia uses in my opinion the blue for the simple reason of the national colors of Gallia: blue and white.
White is for the monarchy, blue and red are the colors of Paris. I guess that is why they keep white and blue for Gallia. These tow colors work well together. And red with white is not really nice. Or I forgot Red and yellow for the Council