Now I mix a neutral color just darker than the ground.  It can be raw umber and ultramarine blue with no titanium or it can be burnt umber with some other modifying color.  It can even be black with some yellow or some other form of a moderate grey or grey green.  The main idea is to begin to develop an under painting in a monotone, usually grey, that will develop the painting into what is called a grisaille, which is pronounced gri – zi.  I like to use a colored pencil to go over my complete sketch, thus transferring a copy to the canvas by means of the paint mix described above or with charcoal paper, or even by covering the back of the sketch with pencil rubbing.  If you use the paint, you can leave it dry completely to protect the sketch.  But I like to begin softening the edges and developing the form with this layer.