I can offer no help regarding spraying but bought mine off flea bay and could choose around 8 different colours. The silver matches almost perfectly.
I would guess you would have to take them off and have them sprayed at a garage, what colour is your car? a body shop should be able to do this easily but you may have to pay a set amount for the paint to be mixed even though you only need a tiny bit.
What type did you fit? What was price and performance like? I was thinking of fitting some one day. Can you retrofit front sensors? I've only ever seen kits for the rear.