Please read this more than once.
Making a single color study is a valuable tool for any medium. It is a powerful first step toward abstraction. it can reveal the compositional relationships between shapes. It can measure the role of color temperature in creating an illusion of space.
Like most studies, monochrome value studies begin by locating the major shapes. Drawing helps, but don't get carried away. At this point we need to know where the shapes are, not what they are. Struggling to identify the components prematurely leads to overpainting and to a degree of complexity that is often not necessary.
Choose a color that can get dark enough to represent black. Dilute with water to lighten your color, and enrich with pigment to darken it. How many steps your value study takes is usually determined by the complexity of the source image.The relative simplicity of this image suggests a three step study;