Pretty sure all the monitors were always color. They were playing back the red alert signs from TMP, weren't they? And all of those painfully low rez graphics in SFS were color, like the ones showing a life form down on Genesis. In fact, the Genesis graphic on Spock's monitor was the same as the graphic seen RP'd in sickbay on TMP, and that's not got much color (blue and white) but it ain't black&white.
I think there's less color in most of the TFF ones, or at least a more muted range, which would be in keeping with the color scheme. I always like that the TFF bridge is one that conforms to Joe Jennings' dictum about having someplace different to go visually when the alert starts or the meteor is coming, because when the TFF bridge goes on red alert, it practically becomes a whole different environment, whereas TUC's bridge looks pretty much the same, just with a red tinge.