A color is first applied very thinly - you will notice how the excess dye as either dabbed off on the rag or smeared off on the brown paper.
A second darker color, in this case a cordovan brown, is applied mainly around the edges to start the two tone effect. It is also applied over the red dye in the center, but ever so thin.
This technique is essentially a dry brush technique with a rag.
The third color to be applied is black - it is rubbed on just around the very edges and then blended in with a rag that contains the red dye.