Can I add another paint color after topcoat?

I painted my countertops a couple of years ago. They have held up great. I did seal them with the water resistant topcoat. I’m thinking now I would like to add another color or two in the mix. Then reseal again with another layer(s) of topcoat. Is this possible? Do I degloss over the existing topcoat and start again? Any help would be appreciated. Thanks!