Derwent Watercolour is a watercolor pencil from Derwent, a British pencil maker. The core is fairly soft. You can color with it dry, or dissolve it in water and use it like watercolor paint. The colors are softer and less vivid than Derwent's Inktense, and they suit delicate work.
The range has 72 colors. Sets come in metal tins of 12, 24, 36, and 72 colors, and in wooden boxes of 48 and 72 colors. Single pencils are also sold.
The color does not become permanent when it dries. You can wet it again later to soften it or change the shade.