Doing color on boards is much easier now on the computer.
Back when each story sketch was drawn on paper, it was important to find a simplified way to add color so that you could get through several panels and not have it slow you down too much. I don’t use color a lot but it helps “pop” drawings. It’ll draw your eye to a story point. Color can set a mood or assist in telling a gag. I’ve mostly used color with songs or with comedy. And I’ll try to use only one or two colors, just to keep it simple.
Here’s a few of my sketches from Hercules.