This was a block of the month with my LQS. How we did this:
At the first of the year, each participant blindly drew a crayon out of a tin. We would need to then bring 1/8 yard of that fabric to our first class and make our first block (we were given a requirement of the quantity of black & white fabrics also, for the whole year). My first color was brown. I probably scowled when I drew the crayon, but said, I'm up for the challenge.
So everybody made block one; each had their own accent color. At the end of that class, we each drew another random color crayon. That would allow us to find or buy that color before class 2. And so on. At this point, we have participated in 12 classes.
Everybody's quilt will look remarkably different from the others, because, first and most obviously, everybody picked different crayons. But not so obvious when we started, was that everybody could put their 1/8 yard of accent fabric ANYWHERE in the block. So if one person chooses a white background with dark points, it will look different from somebody else's block if they make a dark background and put the values in different places.
So, I know someone observant will notice that I have 13 blocks instead of 12. Most people are putting their 12 blocks in a straight setting, 4 rows of 3. I wanted to make my finished quilt a bit bigger, so I determined that if I made another random block and set the blocks on point with setting triangles, I would have a more useful size quilt for my teenage son.
quilt top on floor
some block detail
center block - dark indigo accent color