Colored Pencils is one of the easiest media to handle since they're pencils and you can control your strokes well. There are also a lot of available colors to choose from. First, cover the entire drawing with light strokes. Then, you can proceed with the thick lines to add texture and effect to your drawing. You can also add some more details in your drawing like this one. Soft pastel was used for the blue shadow_effect.
This art therapy trend has yet to hit America, but because publishers have found it immensely profitable, it's probably only a matter of time before you find yourself shopping for a new box of crayons. And hey, why not? Coloring is a fun and joyful activity that is a much easier way to reduce stress than, say, dragging yourself to the gym. It just might get awkward if your friends find your completely finished Benedict Cumberbatch coloring book.