First time I did it, I just hit it with some flat black spray paint; it flaked off in a matter of hours.
Second time I sanded it down, primed it, and then hit it with the spray paint. Don't remember what brands (as I'm not near the bottles) but I used stuff that said it stuck to plastic.
Before I painted it, I just flat out removed the pony, and it just doesn't look right...it needs something to fill the space.