politics; why Republicans are red and Democrats are blue?Also red is better?

Red for Republican
Blue for depressed

Kinda makes sense.

I read a story awhile back that said, previously, the colors were switched. In any case, they're pretty contrasting, so it works out well for images.

Republicans this time are associated with Russia ...

Oh that's just because it used to be red and green on two channels and they picked red for 'R' , and on a third channel they copied the British system of left being red and conservative being blue , and people got confused so they standardized it with the two channels use of red and kept the third channels blue.