That is a very classic subject, suitable for a mural that will last a couple thousand years. Tip; If you wait for the colors to sink in you can change from white to black and back to white again. That means an even colored background by painting right over the vines with the background red color, letting it absorb, then painting over the red vines with green. Darken the shadows of the green with a clear, transparent limewater and PR122 magenta wash.
Thanks for the homemade cookies, they go nicely with your picnic basket fresco theme.
Q. What colors darken brown? A. Ultramarine blue, cobalt blue and cyan blue.