Off the top and rocker, Red and Blue are primaries in the RGB color space TV uses, and I wouldn't be surprised if they give the highest contrast thereon. Since it's the map I guess we're watching--if we're wathching--all night, the graphic should be clear and easy to read. Maybe the blue is blue blood (is California a blue blood state?), but I wonder if blue doesn't just frame red better than red frames blue, at least as far as that urgraphic artist was concerned.

It's a thoughts.