Whatever color looks the most like raw cast iron right out of the foundry with hemi orange paint dusted over the upper half like the factory did.
Have not tried this product, but supposedly it's good stuff.
https://www.cerakote.com/shop/cerakote-coatingOne way to make the coating, and any orange overspray if you do that also, more durable on manifolds is to coat the inside of the manifold opening with a ceramic coating, especially where it bolts to the heads. It will reduce the heat absorption enough that only a slight paint discoloration will be all you get vs burning. Even basic header paint will work for this. Manifold has to be clean for it to adhere so you have to clean them really good inside and out.
