Many artists complain their colors appear bleached or lack strength. Thus, they do not get greater depth in their paintings.
I have certainly complained when my watercolors lack life. Over time I learned to combine dark umber and ultramarine when I want a warm dark. After time experimenting with this combination I can say this dark has transformed my painting.
In almost every painting I drop in this color combination, whether it is at the foot of a woodland edge, the trunk of a tree or the edge of the lawn etc.
Nevertheless, I am often searching for other darks to utilize in my painting. This purplish color above is the result of combining ultramarine blue/alizarin crimson and burnt siena. The jury is still out on this dark but I embrace the variety of options for when the right opportunity presents itself.