Changing values

I've known in theory that a successful composition is based on a play of light, medium, and dark shapes, and that what you see in your subject is only a starting point - you can rearrange those shapes, attribute whatever values you want to them for the best composition, and it does not necessarily end up matching what you saw. Today, I FINALLY understood that, and applied it. I am so excited - I can trace back the journey I took and see how it all worked.
This was done plein air at Hidden Villa, Los Altos, today.
Here is the building that caught my eye. Why? Look at the stunning horizontals - these stripes, this pattern of lines running across - from stairs, to railing, to vents in the gable roof - so intricately designed. But, it is all so dark. Only the eye can discern the shapes and shadows.

I looked for the light, and caught two dots of it on the metal corrugation of the roof on the right. I had no idea where I was going but I started to sketch the shapes to make a value/pattern plan. As I was shading in the dark trees, I realized that the gentle, delicate, skeletal structure of the building and the horizontals could be the lights. Interplayed with the darks, they would be very striking.

Now, the painting. I played with combinations of colors and created a color palette. In other trials, I varied the brown and the yellow but was finally pleased with this muted olive green that the yellow and blue made, and the grey that the blue and brown made. Here is the final watercolor of Hidden Villa Hostel. I am pleased with the color palette, and the shapes, and the tree, especially. A lot of negative painting, which I love doing - carving to reveal the shapes. I also like the implied grass in the front.