Fudge has this beautiful, rich copper coat. Rendering that was a really fun challenge that required layers of watercolor underneath about seven different colors of NuPastel and pastel pencils. Various reds, browns, a gold tone, and even a couple blues. No, really.
First stage, above, I've got the basics all drawn in, using a terra-cotta colored pastel pencil. These erase easily and are a good color that blends right into the coat color of just about any horse.
A bit later, I've added watercolor and some shadow areas, which are a combo of watercolor and dark pastel and carbon pencils. The watercolor layers help me establish light/shadow and add a nice depth to the pencil and pastel work.
Above is just before I put the blue/gray/pink shadow line down the middle of Fudge's blaze, to indicate the shape of the nose bone. Generally I put shadows in first and then work over them with the lighter colors, saving the brightest highlights for last. That's how you get a strong sense of solid three-dimensional form in pastel or in oil paints.