Tried some experiments in coloring with that beautiful Tiger and Bunny original sketch that has Kotetsu and Barnaby in a suggestive pose (nothing definitely "ho-yay" but considering it's original art, yes, it is suggestive).
WARNING: 4 pictures of considerable size under the cut.
Preview:
The original art.
First try: plain shading, totally done in Photoshop.
Second try: added some light, darkened some parts of the shading. Totally done in Photoshop.
Third try: coloring and basic shading in Photoshop. Used Autodesk Sketchbook to add more detailed shading and lighting.