Painting in open shade can sometimes be and often is a most frustrating experience of color contradictions. Predominantly, the color temperature, as it relates, is cool lights and warm darks, however this can easily reverse itself back and forth because of secondary light sources reflecting into the shadows.
As a vantage point, open shade is the best choice from which to paint. It’s far better than placing a canvas (or whatever substrate) in full sunlight. However, when painting in open shade, the light generally is very cool, since it occurs in sunshine on a clear blue sky day, and the light striking the canvas is mostly blue.
If the subject is in bright sunlight (such as a portion of the painting above) it becomes somewhat confusing to judge color temperature on the cool light of the substrate (white paper, in this instance). All I could do, sitting under the shade of a tree, was attempt to work out the various confusing colors in a loose manner as they related to each other. I painted the picture in a studio later on while trying to decipher the color sketches made on site. While making the sketch and color swatches, my only solution was to make all the warm colors a bit warmer to make up the cooling effect of the blue light hitting the paper. Under the shade, the light seemed to alter the cool color mixtures, making them seem more blue than they really were. I attempted to paint them as I saw them and later adjusted the colors in a more balanced lighting of the studio. This was years ago, and the jury is still out.