if its anodized you can try engraving it directly, some colors work well for this. or use a product like thermark or Cermark that you spray on and laser-bond to the substrate. Its a bit pricey though, some try moly spray.
Hey Joe thanks, I will take a look to it and google about it.
Another possible way, may could be to add a self-adhesive foil and then cut them. Remove the parts that I will color. Corlor it, and remove the foil after it is finished completly …