For this drawing, I added colour to the lips using the wacom. I did this by creating a new layer and located it above the photo layer and under the line layer. I then changed the colour, by clicking on the colour palette on the right hand side. Then I painted in the lips.
The advantages of using wacom for colouring were that, you can go over the work a again to make the colour darker for the parts that need shading. The disadvantages were that for the parts that I didn’t want to be darker, I had to rub them all out and start again.