As I recall, the GOP color was always blue. When Reagan won in 1980, the board was described as a "sea of blue". I think that social research showing that blue has a calming effect, while red inspires aggression, caused the networks to switch to blue for the Dems. That, and they saw the Marxist connotation, and in an era when they didn't like being called liberals, and when they were supporting the communists in Nicaragua, Cuba and wherever leftists had a grievance, they decided to change the colors on election day maps. It is just another example of MSM propaganda politics.
I would like it to be switched back. The MSM never would, but Fox could. It would be another way to distinguish themselves from the herd. Then, when we win, it's not a lake of fire, but a sea of blue, once again.
You are correct, Blue was always the republican color as in true blue republican or bleeding republican blue and the Dems as far back as I can remember always used red. It has been only the last few election cycles where it has changed from blue to red. I suspected it was because of the commie association and I think it’s pretty well confirmed.