I do recall some black and white Warner Bros. cartoons being colorized, (mostly early Porky Pig shorts) well before the 80's. The color versions were less detailed than the originals I finally saw much later, so perhaps they simply traced over the original footage.
Even though it was done in the 80's, I think the colorized Fleischer Bros. era Popeye's were done in a non digital way as well. They couldn't deal with the intricate "live" three dimensional backgrounds some of the shorts had at all. I doubt those color versions are shown on tv anymore, but they were real abominations.