I have finished this painting. What I have learned from this project was how to control the chroma of the color. Any color has 3 attributes: hue, chroma, and value. To make the hue and value correct is not very hard, but visualize chroma precisely is not easy. We might be able to estimate how dull or vibrant a color can be, but it is difficult to get it accurately. I had to use measurement and math to get it close to right. I took many photos of the painting during its development. The load the photos on the "painter's guide" app. I measure the chroma coordinates of colors in specific area, and then compare the reading on the corresponding area on the reference photo. The result was shocking to me that how inaccurate I got the chroma. Very often, I tend to make the chroma too high. Now I have gained more chroma control.
I also made a Youtube video of this painting. Please enjoy.