Many people had color monitors in the 1980s. For values of "monitors" that include television sets. The Commodore 64 and Vic 20 were color, as was the Tandy CoCo. Lots of others as well.
For PC connecting to monitor, CGA was introduced in 1981. I'd say by 1985, it was a very popular choice. Before that, many home computers that connected to television were already color.
For home machines most of them would have been colour by 1982-3. My first paid for job was Turbo Pascal on a CGA PC in 1984 so it was pretty wide spread.
I had an Apple ][ GS back then. Actually, I still have an 8088 with a color monitor and such, but I haven't got it set up, so I'm not even sure if it still works.