Step 1. Create a two value statement by squinting at the subject and dividing all the forms into just one dark and one light.
Step 2. Stain the entire underpainting with a diluted mixture of burnt umber and cadmium red. (You can substitute burnt sienna instead of the umber/cad red mixture.) Dilute your mixture with just water or an acrylic blending medium. Allow the paint to dry.
Step 3. Using a limited palette, mix and apply the various home colors. (If needed, see prior posts for help with limited palette color mixing.) Try to mix your desired colors on your palette. Try to mix the correct needed hue, value, and saturation on your palette before appling the mixture to the underpainting.
Notice how the warm underpainting shows thru the subsequent layer, unifying the colors over the entire painting and at the same time creating a sense of sunlight. Make sure you include the needed hard and soft edges to add authenticity. Notice how the established light/dark relationship from step 1 has not been compromised.