Why did my dogs grey and auburn hair grow back black with a different texture?

I had to be careful when I was showing my silver standard, Any injury would cause the coat to come in black (she was born black and changed to silver ) and it was a different texture too. It would take 18 months for the area to go back to normal (if at all). The colour is darker because the area was injured so more oxygen got to that area to aid in healing. It is very common and if the skin is damaged it may not go back to the regular colour.