Please bring back the old overlay feature

Mark, could you describe the process of recoloring the SVG icons with the new overlay feature? Which software do you use, and how do you change their color?
A step by step description would help us find the way to solve this issue with recoloring.

We are already changing the way backgrounds for the subicons are generated. It will be reverted to the old way, like it used to be with the old overlay feature.