I just got the Holiday in Balmora and Grazeland's Gentleman Farmer costumes. Atmoran Bronze in the brown hues comes out dark blue on all parts of the costumes. I spot checked on the Brilliance Brocade Robes and it works fine on them as a rich coppery brown.
Adventurer Brown does come out brown on the Balmora pants and boots (the difficulty of dyeing the top has been separately addressed on the forums), so it appears to be an issue specific to Atmoran Bronze.