My artist friend who runs various classes recommends pastels on mid tone paper - so you start off with an interesting coloured background, like burgundy, or blue, or burnt umber, and then build up your colour over that. Then you can make use of the paper colour too, instead of completely concealing it.

I had a go in one of her classes and my first one (when I was listening to her instructions!) was really effective.

This was a day workshop, and the second two pieces I did that day are nowhere near as good as this one was! She made us put down the highlights and light areas first - which works well when you're using this darker coloured backgrounds. I've seen people use a similar technique with painting too - covering their canvas with a wash colour before they start.