Your pic link is busted! But a GIS for pictures makes it look pretty cool, right in keeping with the period.
I guess it depends on whether you think sky pirates should be colorful or sneaky.
I always imagined that sky pirates pick their prey by circling at low altitudes, looking for aircraft above them. Then they quickly climb to intercept, or climb above and behind the target before diving out of the sun. So I'd paint the upper surfaces in a camouflage pattern, and have the underside painted in something bright and impressive--red and white bands, for example.
Or, alternately, they circle high--in which case you'd paint the underside of the plane in soft blues and grays, and the upper surfaces in jolly rogers and red skulls and all sorts of impressive patterns.
But the paintwork should be patchy up close and the engine should have sooty and oily streaks coming off it. A pirate doesn't always have time to re-do the artwork or keep his plane in the best running condition.