Colouring pages with Procreate

How can I use Procreate to separate a line drawing from its white background?

There are two ways of doing this that I know of. One is quick and easy, the other is a little more in-depth but also very easy to accomplish if you follow each step.

For all intents and purposes, these two methods are just two different ways of doing the same thing for the simple purpose of colouring an image. 

If you're working with a multi layered illustration, you'll have more complex decisions to make considering your other components. I would suggest that the second method is the way that really does what you want to do. The first method is just a quick way of manipulating the layer settings. 

Method 1.

1. Select the layer you want to prepare.
2. Duplicate the layer.
3. Switch the top layer's setting to Linear Burn.
4. Colour on the bottom layer.

Method 2.

1. Select the layer you want to prepare.
2. Copy the layer (go to Actions, select Copy).
3. Create a new layer on top of it.
4. Fill the new layer in with solid black.
5. Create a mask layer for the black layer.
6. Paste your image to the mask layer.
7. Invert the mask layer.
8. Merge mask layer and black layer together.

You should now have a new layer on top of the original image that consists of the line drawing on a transparent background.

Keep your new layer as the top layer and add as many colour layers you want underneath it. 

Now you can colour in the image any way you want and the line drawing will always stay on top and unaffected by your colouring.