>>1818263I use
Paint.net to do it. Four layers in total; the Background, the Coloring layer, the Outlines layer, then the layer with all of the colors I'm going to use on it.
Paint.net also has a Black and Alpha adjustment to get rid of all of the white in the Outlines layer. It's pretty helpful.
... It was really time-consuming, but I found it gratifying.
>>1818132Thank you; I hope they see it soon so you can get an answer on that.
>>1818240Like this red?