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I honestly don't know why showing the conservative/right side as red makes any sense. It is the left that pushes toward collectivism, socialism and communism.
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2 reasons normally, possible 3 in this case:
The left are liers, changing the color is subtle propaganda, just like how most communist countries have the word "democratic" in their name when they have nothing to do with democracy.
The colors red and blue are also traditionally used to signify friendly and enemy forces, blue are the good guys, red are the bad guys and the left runs the media so they put themselves as blue, again, subtle propaganda.
In this case there may be another reason as well, Britain traditionally is associated with the color red, "the red coats" and the EU has a blue flag.