Before the thread comes to an end, can anybody tell me why the herring should be red? I've seen a lot of herrings, but never a red one. In the original phrase about drawing a red herring across the trail to confuse the dogs, the dogs couldn't tell or care what color the herring was.
Maybe this is the answer:

A herring that has been dried, salted and smoked turns a reddish colour.
These cured fish have a particularly strong smell, so in medieval times
they were useful as a lure for training hounds in stag hunting.

Later, people who were opposed to fox hunting would drag a red herring
across the fox's trail and entice the hounds away from the scent of their
quarry.