After I put in the order for my chicken tacos, I get out the gouache. Just four colors: ultramarine blue, flame red (Daler Rowney), burnt sienna, and white.
There's a stop sign catching the full sun and a brick building in shadow just beyond it. I'm painting over a casein base layer tinted to yellow-orange, and using a dark blue colored pencil for the first lines. The horizontal line through the base of the stop sign is the eye level.
At the end I bring in a little white Nupastel and light blue colored pencils for the lines of the bricks. Gouache presents a very receptive surface to chalk and colored pencils.
If you're ever passing through Kingston, New York, I can recommend the great homemade Oaxacan food at Just for You Mexican Restaurant