I assume you're talking about horizontal lap-siding, not steel siding like is on barns and sheds.
That said, yes you can repaint it. The key is surface preparation and primer.
Talk to somebody at a paint store - and by that, I don't mean the 18-year old kid that's mixing paint at Home Depot. I'm talking about somebody like and owner/operator of a Sherwin Williams store, or something like that.