As I promised, today I took a photo of the outcome from the last class at Pratt. In this smaller format, this looks much better than the real painting. The key was two back-lit umbrellas. Since I tried following the condition not mixing those 12x4 colors except with white, the darkest colors were green, ultramarine blue and purples. By keeping the local colors and not to go far away, entire painting became very light as you can see easily. Also due to my set of primary colors which are transparent, the painting looks transparent as well.
I stopped painting this in about 3.5 hours. No break. So, I was tired at the end. But the outcome wasn't too bad to me. By the way the canvas size was 22"x26".