Now, it was time for one of the most important points: the colors. The technique I use is similar to what you use when working with traditional oils or acrylic paint. I work from dark to light. At this stage, it's very important to choose the right colors because the drawing is built upon this color palette.
I changed the layer of the sketch to Multiply mode (by doing this, I can paint beneath the sketch) and placed another layer under the Multiply sketch layer for the basic colors (Fig.03).
Mini tip: I always paint small directional arrows on a separate layer. They show me where the light comes from and where the shadow has to be.
Amplify the Picture
The drawing looked a little bit more alive now than it did before, but it was still far from being finished. I created a new layer in Normal mode and thus painted above the sketch. I prefer messy-looking images to perfect ones, so I used different brushes to create that effect (Fig.04). Mike Nash, who is an amazing artist, offers a lot of fantastic brushes on his website for free: http://www.mike-nash.com/tools/
Using different brushes gives the drawing a more artistic look so that it doesn't look too digital. During this stage I think it's important not to draw in too many details; the most important things are the atmosphere and lighting (Fig.05). Therefore I didn't zoom in on the picture so that I had a full view of it. With the Color picker I chose the basic colors that I had already devised and changed them to that effect. I used a lot of different layers for that because if I made a mistake, I could then very easily and quickly correct it.