I'd say better. One insect on this side of the pond seems to prove the point. The Large Dark Olive (Baetis Rhodani) has very bright yellow legs (at least the ones on the River Ribble do). However the best imitation of them I've found use golden badger or grizzle dyed yellow olive. The hackles with two colours seem to work much better. So I'd prefer a furnace to plane brown any day.
Cheers,
A.