Mono Means One
Yep, a monochromatic painting with one color plus black and white. This is an excellent exercise to practice on depth and perspective.
You can get many values by using one color and adding some white, and some more white and well you get the picture. Then you do the same thing with the black. Take your color and add a tiny big of black, and then a little more and on and on, (Just remember that adding black to yellow makes green so you might want to choose a different color.)
Doing this practice will really help your eye to start picking out the values and will improve your overall painting.
Have a ball using this practice.