According to Ray Bergman's "Trout", originally published in 1938 the pattern is as follows:
Body: White chenille.
Hackle: White (probably cock).
Wing: Cardinal (probably duck or goose depending on size).
Bergman comments that it's an effective Brook Trout pattern.
The all red pattern that is noted as "Cardinal" in Veniard's "Fly Dressers Guide" (1954) is named as the Scarlet Ibis in "Trout". The dressing (in Trout) is as follows:
Tail: Scarlet (probably duck or indeed ibis).
Tag: Gold tinsel (flat).
Body: Scarlet floss.
Rib: Gold tinsel (flat).
Hackle: Scarlet (probably cock).
Wing: Scarlet ( probably duck, goose or ibis).
So, who's right? Given that Bergman was a very well respected US wet fisherman and given his book pre-dates Veniard's I'd go with his pattern. However, his dressing of a Watson's Fancy shows the red half at the front of the body while the modern, and Veniards, concept of the pattern has the red at the tail. Again, I'd go with Bergman as to me (purely subjective) a red front half makes more sense.. Also, I've noticed a few instances in Veniard where the given pattern doesn't completely match the corresponding picture.
Your best bet Gerry would be to go to the US based
Classic Fly Tying Forum and ask someone like Don Bastian, he's a Bergman nut. You'll likely get good answers from the likes of Ted Patlen or one of the admins called Isonychia.