What paint should I use for bare radiator pipes ? Thank you in advance?

High heat paint for exhaust manifolds(for cars) so can be got at an auto parts store or a HOME DEPOT store. Brush it on. Silver works good. Follow directions on the can.

High heat paint your choice of color.

Yeah - use a nice metallic silver enamel to reflect the heat back into the radiator - NOT.

Been known for years that those gold, bronze, silver, copper etc radiator paints drastically reduce the efficiency of the radiators. But maybe OK for the supply pipes, but would be better to insulate them.....lots of pipe insulations available these days - not the old thick asbestos stuff.

I'd ask a HVAC company what they would recommend.

Use "metal primer" first, then any color you want

Radiator paint - unfortunately usually only available in that shabby kind of off-white. If it fits your interior, you also might try stove paint, if you like black or metal grey better.

The problem is that usual paints aren't heat resistant enough for radiator pipes in the long term.

In the UK Hammerite make paint specifically for radiators and pipes. If you are elsewhere any good enamel paint will work.

Gold. Or silver probably silver if we're being realistic or copper.