That timescale pretty much ties up with the launch of 32 bit QuickDraw (April 1989). Graphics card manufacturers had created 24 bit colour boards before that date but each one implemented the functionality in a different way. Software developers had to write around the limitations of Color QuickDraw to get 24 bit colour, and they had to do it for every card. Development speed was limited until 32 bit QuickDraw on System 6 created a new standard. Then colour really took off.
Does anyone recall the test image of a frog that was used to demonstrate the ability to print green on a dye sublimation printer?