Leigh...if I'm really getting one of those girls I need to get a dark colored NON-CRESTED roo too. Preferably not related. But I'll consider anything.
the key wouldn't be so much DARK as no wing triangle... the roos won't be dark like the girls in a birchen-based variety...
brown-red bantam cochins (image found on google images) just for an example...
for examples of the wing triangle, look at a black breasted red bird and a brown-red of the same breed, side by side. (or silver duckwing and birchen - silver versions of the same thing) birchen is known as crow-winged also.