What colour of show lead should i use when showing my jet black cocker in the ring?

My instinct would be to go for black, so that it doesn't detract from the dog.

Yes me too, but don't wear black trousers.

No, never wear black trousers (or in the case of showing a dog on the floor, a black or dark top) when showing a black dog! :)

I have black Flatcoats and I never wear dark coloured trousers for showing.  You will get to a point where everytime you go clothes shopping you will think 'could I show in it?'  My husband says I'm obsessive!
If you do wear something dark, the dogs legs get mixed in with yours when you move the dog and it is sometimes difficult for the judge to seperate them, especially at a distance.  :)