When working a really big or deep place with double number ferrets in i find it handy to have different coloured ferrets so you can see who is showing at the holes and you know if one hasn't shown for a bit without walking all over the burrow . Once we tried marking albinos with different felt pens between the shoulder blades after 5 minutes in the box they came out all the colours of the rainbow and we couldn't tell them apart LOL , That's the only reason i would try to breed silvers as you can get a colour range from light sivers to nearly polecat markings