You will recognize a pastel sketch easily. You can really see the chalk lines and the sketch lets the paper show , so the colour of the paper is very important. This technique gives a lot of movement and strength to the artwork.
I sketched a naturist friend at the wild coast of Quiberon and I cheated for one of the portraits, she had tanned a lot I modified her hair I made it long and straight and I invented a waterfall. That’s the advantage of graphic art, you can remove and add elements .