Well they call it Concentrated water color ( USA spelling Grrr ) But it works more like ink. I have had favourite colours like Slate blue and Tobacco brown for years. The colours are so vivid and in your face. Took a bottle of Pumpkin to life drawing...
Initially a bit of a mess, but then it calmed down and I got some actually drawing done with it. Was using the pipette to draw with so I could control ( sort of ) the amount of ink coming out.
Finished off later when the ink had dried by knocking out the background colour to bring the figure forward.
The model, incidentally, was the same guy who was on the BBC's 'The Big Painting Challenge' the other Sunday, demurely pre watershed in a loin cloth. Hehe.