For the next few limited palette posts, I'll be using Blockx watercolour.
The colours for this limited palette are Gamboge PY6, Crimson Lake PR264 and Primary Blue PB15:3.
This is a rather versatile palette capable of mixing vibrant orange and greens. The limitation is the purple which is rather dull. When the three colours are mixed together, you can get nice neutrals and black.
The colours are quite transparent so they are good for painting over pen and ink.
The grays and the neutrals on the buildings (left) are mixed with the three colours. You can charge in Crimson lake to make the mix warmer or Primary Blue to make it cooler or more gray-ish.
The black car was mixed with the three colours in concentration. Greens were with Gamboge and Primary Blue. Crimson Lake was added to make it darker.
The colours are really vibrant. Blockx watercolours are pretty high quality. To make this palette more versatile, I would include Ultramarine so that I can mix vibrant purples.
All three colours are non-granulating so if you want to create textures, you have to use brush effects.