The colour thing was never set in stone but from what I read the general practice was to give blue to the party of the incumbant and red to the challenger. The trouble is the 2000 election is seared into the minds of the dims and seems to have made the colours permanent now.
Not true. In fact, a lie calculated to take the heat off the MSM for the switch.
I’m going to pull out my conspiracy theory and tinfoil hat and say the MSM delibrately manipulated the color change, because they were stung too many times by people making the comparison between the “red” democrats and communism.