Pencil drawings can be added to your cover or spine design using the 'PENCIL' option shown on the menu at the bottom of the Cover Design Tool panel.
Pencil Colour
Select the 'PENCIL' option and change the colour using the 'STROKE' option.
If you need to change the colour of an existing pencil drawing, select it and change the colour using the 'STROKE' option.
Pencil Size
Select the 'PENCIL' option and change the thickness using the 'STROKE WIDTH' option.