Sounds like an interesting project. Is this theory based, or will it be executed? Also, are we talking about one backpack or hundreds? That could make a difference in how cost effective working with some suppliers would be.
As for materials, most outdoors materials are not made into very exciting colors, but I have seen some of the XPac fabric that Dimension Polyant makes make in brighter reds, greens and orange. You can see some info on a seller at Rockywoods.
They make for some very nice looking packs. I'm not sure what other colors they make. Depending on the size of orders, some companies will allow you to choose a color, but you have to order quite a bit of fabric.