In the Marines, we didn't refer to "white" and "black" Marines. If you were describing a Marine to someone, and it was necessary to describe his appearance, you'd say "light green" or "dark green". What that meant was that we were all "green" (meaning Marines), and that was the most important thing.
So if someone wants to talke raise and political affiliation, it would be "light blue" and the "dark blue". But the most important thing is that we're all Blue.
I think he meant Blue like in Blue States. I am certainly not a Blue Stater