Is the engine free air cooled (no fan moving air across the engine) If it isn't water cooled, I would strip off the paint regardless of color. Seems to me that anything on the surface of the engine would inhibit heat transfer to the air. If its a water cooled model, i would think it might run a bit warmer but it shouldn't make a difference.
2001 Magnum 325 with a blown engine; rebuilt 2004. Broke timeing chain 2016 rebuilt again and still running. Warn winch and Moose 60" plow
2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. 12x7 front, 12x8 rear, QSC Clutch Kit
My Trail Machine:
2004 Sportsman 600 Twin, 25" RipSaw Tires on stock steel wheels, Moose rear box
Completed Project machine:
2001 Magnum 325 MOSE with a blown engine. Transplanted a 2005 Magnum 330 engine. Committed suicide on the trail Oct 2016. Spun Rod Bearing after oild cooler line failure. Rebuilding Engine.