You will still need to add the Liquid and CSS necessary for getting the chosen color to be used by your theme.
For the custom color in the sections I believe you should be able to utilize the code from that “config/settings_sheme.json” file within the sections themselves for adding a color input. You still need to make sure that the CSS for the them utilizes the color you choose via a mix with the Liquid code.
Sorry it’s not a more direct answer than that but that is what else you will need to do to make it happen.
Hope that helps!