EAGLE IN FLIGHT
One of the challenges I presented to my students was to paint using a limited palette of ultramarine blue and burnt sienna. Blue and orange are complementary colors - opposite on the color wheel - so they look great next to each other and when mixed you can get a wide range of nice grays and a really dark neutral color. Limiting yourself to two colors will force you to focus more on the values - darks and lights - of the overall painting. Ready to give it a try?