Green and Red Still Life Objects (the color of, and the complement of, the color of the pastel paper). Black and white is an option too. 

Possible subject matter: a potted plant with/ or without, flowers (you can make them red) – or red peppers, green peppers, red onions, scallions, red pears, green pears, red apples, green apples, limes, etc., or pitchers and mugs (anything in the kitchen) that is red or green using Alphacolor color pastel chunks, pastel pencils, and a pencil sharpener, a pink pearl and kneaded eraser, on light green pastel paper (half sheet). Or you can use just black and white on the green paper or the sketch paper.