Oh Goody!! Rae is at it, again!!
Ponyhair is not really from ponies. It's from cattle. It is made the same way the leather for a sheep shearling coat is. The hair is not removed from the hide as part of the tanning process, and it is then sheared to make ponyhair leather.
The industry name for this product is "hair on hide". It can be dyed just about any colour, but during the manufacturing process it is first bleached to remove the natural colour, then dyes are added to create the colour or pattern desired. Kind of sounds like a trip to the salon, doesn't it. Well, it is, except they don't scalp you to colour your hair.
Any of you who have coloured your own or someone elses hair will know that the finished colour is dependant on original colour, texture, etc.. Hair on hide is no different. You will just have to experiment on the particular piece of leather you have.
Tarrago makes variety of metallic colours and you may have to mix a special batch for your needs.
Well, good luck. Hope I haven't scared the crap out of you and cause you to abandon this project. Remember, "In for a penny, in for a pound."
Go get 'em, Rae!!
Cheers
Julie