I have, for some reason, been under the impression that traditional coch-y-bondhu (or bonddu) hackle was a dark red with black center and tips. However, on p. 212 of Robert Smith's book he shows a photograph of coch-y-bonddu hen feathers that are primarily black with a light gold list and tips. Live and learn as they say.
In ancient times, cats were worshipped as gods; they have not forgotten this.
It's my understanding that it could be any of several variations, depending on where you're from and where you live. As a hackle description, it started out meaning "the right hackle for the coch-y-bonddu beetle imitation" and usually was synonymous with "furnace". The meaning has changed over the years so that more people today use it to refer to black-red-black or red-black-red, depending on where you're from.