Recently, I bought some art supplies from Cheap Joes, There was a promotion going on and I received a free 5 ml tube of Rembrandt Permanent Red Light (PR254/Py154). I wanted to try it out. It makes a light salmony pink, and isn't very strong as reds go, so it's nice for making pink because it doesn't get too dark, too fast.
However, I needed something cooler for the shadows, and it went lavendery gray rather quickly when I added Ultramarine Blue. So I used Quinacridone Rose for the very darkest areas.
As I've mentioned before Quin Rose is one of those powerful colors. It also doens't move very well (which means it doesn't spread much even when mixed with lots of water). This was a painting that lent itself to hard edges, so I used that characteristic, and was careful not to over-blend the edges of my other colors.
The two reds and Ultramarine Blue were mixed on the palette. I used Cadmium Yellow Light, Phthalocyanine Green for the background, getting the varying tones by glazing -- putting down a wash of color, letting it dry completely, and adding up to 4 washes of varying strengths in different areas.
The reference photo I used came from the Morguefile free photo archive.