I've done a couple of ugly fabric challenges.
The last challenge I was in we all drew a thing out of a bag. There was all sorts of things in the bag, greeting cards, food labels, napkins, etc. You had to use the colors in the thing that you drew in the same proportion. I pulled out a really pretty, antique looking Christmas napkin. I searched thru my stash and then thru several quilt stores and never did find the green and red in that napkin. The green had a lot of blue and the red was way to the orange side. I finally gave up and just made a wall hanging that I liked with Christmas fabrics I liked.
I have seen crayola challenges and M&M challenges.