it was the same box with a label that said "Brighter Screen"....most people wouldn't even pay attention!
plus they only made them in charcoal grey and i think they were a bit limited since they came out towards the end of the GBA life.
EDIT: i guess you're kindda right, though the box change was subtle...
EDIT 2: the moral of the story, Sony needs to do the same with the PSP-3000 (minus the box modification)