Covering the cable with black techflex may be your safest and least messy option. Some versions of techflex have a less open weave and will look than others, the kind with a softer hand to it (can't remember what they call it, feels more like cotton, probably polyester) has a tighter weave and is more comfortable with less abrasion to it if you are wearing them.
If you decide to paint them, I'd use upholstery paint, available in spray cans at autoparts stores. It is designed to adhere to vinyl or fabric remain and flexible and not crack or peal after drying. Be careful to completely mask off the grid and the termination well before spraying!
Sharpie doesn't work very well.