As ubequilting and JimGem's mentioned upthread, a lot of the failure of the quilt belongs to the teacher running the mystery.
I've run several, and I always did everything I could to make sure the instructions were as explicit as possible, so the participants could/would make the appropriate fabric selections.
The color theme was actually irrelevant, but it was my responsibility to make sure that the value and scale of the fabrics selected would work in the final quilt.
Although, sometimes I do have to say, someone would insist on using fabrics that had been in their stash forever, and even when warned that it might not work, still insisted. And when it didn't, I could only shrug my shoulders.
I'm sorry yours didn't work out. But mystery quilts can be a lot of fun.
You just have to really dissect the fabric requirements provided, and if details on the value and scale required are missing, push to get more details.