Load selection and colorise
Back in the Layers palette I create a new layer, load a selection from the Alpha channel (Select>Load Selection> Channel: Alpha 1), and fill the selection (Alt+Del). I now have a layer of opaque pencil lines with a transparent background. Using the Adjustments> Hue/Saturation dialog, I can play with the colour of my pencils, lightening them so that they pop against a dark background. Here I keep it simple and set my new Pencils layer to Multiply.