(R) used to be blue and (D) was red, until the MSM didn’t like it. Then it was a decade or more that the MSM simply reversed it. (R) is red now, (D) is blue.
I guess the color red is associated with communism because that’s the predominant color of communist Russian and Chinese flags. I vaguely remember Dan Rather was the first one to flip colors when referring to Democrats and Republicans. The media being what it is, grabbed hold of that and wouldn’t let go. Doesn’t change what they (conservatives and socialists) are, though.