Shirt & Tabard rules for all challenges have changed. Only white or grey (green for Blood Thirsty) shirts & tabards allowed.
Cosmetic exception gear is also no longer allowed and will get you flagged (green is okay for Blood Thirsty).
These folks have generously donated to WoW Challenges financially. Funds go directly to paying for monthly server costs and helping us keep doing what we're doing
with the site and the challenges. Thank you so much for your help!