I found the reference image for this series of portraits on Pinterest. My apologies to the photographer—I don’t know their name—but the subject is the actor Alba Rohrwacher. I’m using the reference photo for practice rather than for profit, so I hope that this falls within acceptable copyright use. I painted these on ungessoed, unprepared Kraft paper, so I expect the paintings to disintegrate eventually anyway!
In the main image, I did my usual thing, trying to pin down specific color patches for different areas of the face. In the panel of smaller, quicker paintings, I used a monochromatic modeling system that I recently learned about from an excellent video by Kerry Dunn. His demos were far more impressive than you might guess from my attempts here.

I’d like to keep practicing this method, as I think it will be especially helpful when painting from live models. In the videos, Kerry uses thick and thin passages of burnt umber for the shadows, and then another color (usually orangey, mixed with various amounts of white) for modeling the light side of the face. In its simplest form, this is the only color added, but he also demonstrated how and where he begins to introduce other colors into the face. I may not have interpreted his method correctly, so if you’re interested, I recommend following him to see his videos. He has offered videos periodically on instagram, and you sign up in the comment section when he makes these offerings. @paintkerrypaint on Instagram.