With regards to cage colour, I've heard that black is easier to see the bird in because your eyes 'ignore' the 'absence' of colour and focus on the plumage of the bird instead.
My cages are all steel wire though... so I can't confirm that observation.
Powdercoating is probably the safest method -
if you don't prime it. Most primers (they do this before adding the powercoat) contain zinc, which can be deadly if your bird decides to chew on it.
See the following article regarding painting cages:
Bird-safe Painting Tips
Personally, I would AVOID painting the cage bars and leave it to a professional. If you MUST paint a cage, look for the following:
- do not contain lead, zinc or chromate
- are "high adhesion", formulated to bond with the metal surface
- are hard-wearing
- are fast drying
Once the cage is painted, to stop your bird from using their beak to 'climb' the cage, align perches in front of the bar, so they can use the perches for stepping/climbing instead.
Example with ladders against side:
Example with Perches 'laddering' up side of cage
Note: All above are illustrative examples

Not proper cage sizes.