'Hand coloring' a digital sketch

There is a very cool technique in Photoshop where you can turn any image is what looks like black and white pencil sketch. I describe this in the February issue of my free monthly eMagazine, Photo Insights. I took the technique one step further and 'hand colored' it like I used to do with Marshall's Oils on a paper print. This time I used Photoshop, and all the coloring was done where the brush tool was between 10% and 30% opacity because this allowed the details of the image to come through the color. This technique is time consuming for sure, but it's worth it when finished. This took me about 30 minutes. I photographed the costumed models in Venice during carnival. This is one of the setups I do every year for my photo tour groups.