Hi pahun, there are paints on the market to do this just go to one of the big DIY stores and you will find them. Another way to do it is to cover them with Fablon or Fablon plus which gives a harder wearing finish than Fablon. It takes a bit of work to put on properly but the finish is good and you dont get smell of paint which some people are not to keen on. Which ever you decide on make sure all grease and grime is off them first as neither of them will stick properly otherwise. Good luck.