When we start to colour our image, we’re going to be working on a number of layers underneath the line art, so our first step is to get the line work away from the background.

One way to do this is to simply copy the Background layer onto a new layer, fill Background with white, and set the new layer to the Multiply blending mode. This effectively lets us see everything below our line work just fine. The problem with this is that if we had used the Multiply method it would be harder to later composite the character into other documents, and we would have to go through the trouble of masking the art. We want to avoid that, as the real strength of this whole technique is its flexibility. Another problem with using Multiply is that it doesn’t easily allow us to create coloured lines.

Fortunately, isolating the line work is really easy. Do this:

1) Switch back to the Channels palette.

2) Hold down CTRL and click on the icon of any one of the Channels. RGB, for instance. As all the channels look the same right now, it doesn’t matter which one.
This makes a selection in the shape of the content of the channel. We’re going to use that selection to fill a new layer with black. However, if we were to do it right now, we would find that the fill makes all the white parts black and leaves our line work transparent. So…

3) Invert the selection. (Select --> Inverse, or hit CTRL-ALT-SHIFT-I)

4) Switch back to the Layers palette.

5) Create a new layer (click the little button on the bottom of the palette right beside the one that looks like the garbage can, or hit CTRL-SHIFT-N). If a little box asking for a name etc. pops up, just hit okay.

6) Make sure your foreground colour is set to black. (Hit D to set the foreground and background colours to their default Black and White).

7) Fill the selection with the foreground colour (Edit --> Fill, or hit ALT-Backspace). You should see a slight shift in the blackness of your lines.

8) Activate the Background layer.

9) Select the whole thing (Select --> All, or hit CTRL-A)

10) Fill the selection with white (Edit --> Fill, or hit CTRL-SHIFT-Backspace) Now, if you hide the Background layer (press the little eye-icon), you'll see how amazingly transparent your line work is.

Your line art is now conveniently separated on its own layer with completely transparent surroundings. You’re ready to colour.

Next: Colouring with Solid Colours...