I definitely use different colours when painting to create black, red and green make a great black for example and lots of other mixes depending on what colours i have used in my painting, and a small brush is great for adding in black detailling. Unless of course I am creating an artwork with coloured pencils then I use a black pencil. Does that answer your question? All the best
I just had to use black in my acrylic painting and the same applications would apply to watercolour. In using black, it is said that you get a more effective black by mixing your colours for this. If you do use black out of a tube, there is ivory black which is brownish and there is mars black, which is bluish.
The black that I mix is a combination of Ultramarine blue and Burnt umber.
Other combinations are: Prussian blue and Burnt umber and Burnt Sienna
Ultramarine blue and Alizarin crimson and Burnt umber And there are other colour combos too.
I think, where possible, for colour harmony, use at least one of the colours that you are already using in your painting as part of your mix for black. Just my thoughts...
I use cad red and ultramarine blue then add cad yellow to make my black. I will take note of the other combinations stated here and give them a go. Thanks guys. I use ivory black when only a tad is needed in a painting.