This is a little demo I did last week for my pastel class. I wanted to show how to look for unexpected colors. We know the squash is yellow, but what color are hidden in the shadows? In the stripes? In the dark areas underneath and objects around it?
Being the squash is yellow to begin with, odds are it has purple tones in the shadows. Choosing the complement (opposite on the color wheel) as a starting point is usually a good place to start when creating a shadow color. In this case, I’ve used a violet pastel that is a little on the red side, and combined it with the yellow of the squash and a hint of violet blue to cool it down a bit. In the orange areas that are in shadow, I’ve done the same thing only used just the violet blue and a redder, cooler orange than on the stripes that are in the light.
Because this was just a demo, I blocked in surrounding areas with color as suggested by the objects surrounding the squash, some dark green from another squash, some blue from the table cloth, and some orange from a pumpkin. Simple exercises such as this are helpful in training your eye to see color variation. Color variation is one of the most important concepts in painting, it helps to keep your painting from looking flat and monchromatic, while adding depth and interest to shadow and light areas alike.