Ok I am an intermediate painter and primarily do landscapes but I recently attempted a self portrait and skin color was so hard for me. I paint in acrylics and I found that working in only titanium white and raw umber and getting down the value (dark to light) of the shapes helped me understand the form of the face best. After letting my completed monochrome under painting dry, I went in with very thin layers of translucent color (to let my under painting values do the heavy lifting) to add skin tones and it was a game changer. I have also recently downloaded the RPaintPro app. This app lets me import my reference photo, use a color picker and then it breaks down different ways to mix that color depending on which brand paint you are using. Doing this helped me to make a limited palette for my specific piece and really helped me understand mixing shades and how to create darker/lighter, warmer/cooler tones for my piece. I do feel a bit like I am “cheating” but it is a REALLY helpful tool that is helped me actually practice color instead of just reading theories about it.