How To Paint/Colour Metals for jewellery?

I painted some "snap" hair clips with Humbrol Enamel & thought that would be quite durable until I saw that my cat had gotten to one & put teeth marks thru to the metal! Would this sort of paint be ok to paint (minus cat attacks) pendants, etc (made from eg. base metal, pewter, brass). Or is there a special type of paint that I can use? And how durable would it be? Is there anything that I could paint hairclips with that would be flexible enough to withstand constant bending? I'm thinking the enamel may not be a good choice in that instance.