The seat material is different. The center pin of the needles in black on the 2003 and silver on the 2003.5. Floormats, stitching color, shifter, shift boot, pedals, spoiler, fog lights, lip, rear bumper guard, and wheels are all different. The exhaust is different. Under the hood, things are mostly the same, but there are some very slight differences, mostly in making it easier to get to things in the 2003.5.
As for color, 2003 only had black and orange. 2003.5 is in the colors already mentioned.