I think the only way to do it with acceptable results is to colour the stickers before importing them into CAP. Seems that the brightness slider on the layer properties has to be all the way to the left for the colour to stay, but that makes even the black have a colour to it, plus the image loses it's crispness.
I took the same image and recoloured it four times to make different stickers, then I added each of these as a custom sticker. I made a pattern with four layers using a different sticker on each layer. The result in game was nice and clear plus each layer colour can be changed without losing the black.
The only thing, is when using the create a pattern tool ingame to change the colours, the buttons you choose from are all black. You have to select one and just experiment by dragging the colour select tool around the large circle (lucky there is an undo button lol)
This is the original pattern I made using a different sticker for each layer.
Here, I've selected the coloured spot to change the colour on one of the layers. Not sure why only one spot shows a colour.
And here, I've selected one of the black spots. Even though they don't show a colour here, if you drag around on the bottom circle, the colour will change.
Norma