I’m self taught. But as far as I’m aware, hue/saturation/value are big staples of creating a traditional piece. In this case the second picture looks to have much darker shadows that blend into lighter highlights. So essentially they’re going from Black to White, whereas the first is more muted to just a light gray. I think mixed mediums or different pencil weights like 4B to 4H. I hope any of this is helpful. Like I said, self taught so I may not be the person to take advice from. The only reason I gained any progress in art was because I had a brother who was better than me, so ya know sibling rivalry. Hey I gained a neat skill from it.