225 Warm Yellowish Orange
This odd color was only used in sets for one Duplo plate in 2004. There are a few plates and bricks in this color from LegoLand parks. This color was probably intended as a replacement for 36 Light Yellowish Orange, as part of the color change. No one noticed of course, since both colors were so rare.
If anyone has a 2x4 brick to trade, please do let me know, it's the last 3001 I need :)