A helpful depiction, which appears at the Wikipedia article "Red states and blue states," which I was reading in an effort to determine whether it's true — as I'd long assumed — that Republicans got the color red because if red had been assigned to the more leftward party, it would insinuate Communism. I read the entire "Origins of the color scheme" section, and there's a complicated story going back to 1888. ("Grover Cleveland and Benjamin Harrison used maps that coded blue for the Republicans, the color Cleveland perceived to represent the Union and 'Lincoln's Party,' and red for the Democrats.") Apparently, things have gone back and forth, and the current fixed color assignment dates back to the post-Election Day squabbles of the year 2000:
In the days following the 2000 election, whose outcome was unclear for some time after election day, major media outlets began conforming to the same color scheme because the electoral map was continually in view, and conformity made for easy and instant viewer comprehension.Ha ha. Love the super-bland Wikipediaese. Whose outcome was unclear for some time after election day... The election results were so confusing, that MSM decided to bestow some clarity upon us. At least we could understand one thing: Blue means Democrat. Red means Republican. And we gripped tight to that childish simplification ever after.