I sold sequined material this way - had heaps of boxes - left overs from stage productions. They went like hot cakes. The value was about 30% off retail price as the fabric was donated to us by the producers and it was a school fund - raiser. I think you would have to make it an attractive price, but don't give it away. Personally, I would not sort out all the colours as every quilt or project looks better with a variety, and it will be less work for you.
Another way would be to tie them into attractive colour packs as they do in quilt shops, with tape tied around the bundle. That way, everyone can see what they are getting before making a purchase. If you are really clever, you could make up a few jelly rolls or charm packs to display the material. It will look more attractive if you have a market stall.