Based on the description of the watercolor painting, the principle that is likely not shown is radial balance.
- Variety can be inferred from the different elements such as the car and buildings.
- Proportion could be observed in the sizes of the car relative to the buildings.
- Perspective is typically used in street scenes to create depth and distance.
Radial balance involves elements radiating from a central point, which does not seem to apply in the context of a street scene with buildings on each side and a car in the center.