How do I remove paint from pipes?
If the paint is in good condition, with no chips, peeling unsightly blemishes I would repaint. It would be a lot of work to get the pipes really clean. Any exposed thread at the fittings will be tough to strip You will need to scuff the old finish to promote adhesion. Pick a metal color. Rustoleum  has colors like Bare cast iron, nickel, brass etc. You could accent the fittings with a contrasting color. Just be careful when working around the sprinkler heads.