Palette colors for Plein air

I have been trying out a narrow palette of colors to make my pack lighter and to instill harmony in my compositions. The colors I am using these days and starting to really like are: Ultramarine blue, Permenant Red medium, Cad. Yellow Lemon, Naples Yellow Deep and Warm gray. Sometimes Cold gray too as it makes some lovely greens combined with CY Lemon. Oh and of course Titanium White. Making a color chart is the best exercise to help you see what possibilities

are available.