Julius Caesar was assassinated for wearing red boots. Barrack Obama was lambasted for wearing a tan suit. Purple is associated with royalty, white is associated with clergy, and gold is associated with superiority. Red and Blue have powerful meanings in America, and so does Green. Which colour is the most political in your opinion?
Red is associated with social democracy, socialism, communism in most countries; almost only in the US is it the color of the conservative party.
Just like most common standards, the US decided to go full ham and use their own.