Above: "Autumn Fairy - Fifth Stage Paint." by Portia St. Luke
Here, I'm adding ultramarine blue to the shadows. In the places where it's being painted over existing dark brown (burnt umber) it will look black, but combining ultramarine and burnt umber creates a much richer black with more subtlety. Even when mixed on the palette the "black" that results is much truer to nature than straight-out-of-the-tube "ivory black" or "bone black." The artist can control the mix and create a warmer or cooler black by using more of one pigment than the other.