Fun project!
I ruler fold small pieces with a 5 inch ruler. Then fold again in 5 inch folds depending on fabric width. The get stacked on edge so I can see each color. I don't worry about exact color sorting as it's easy to see what is there. No need for extra work to cut cardboard or purchase extra supplies. Easy and quick to do.
These are the bins I use to hold the folded fabric pieces. The medium deep is a perfect size as it measures 6x16x 5 inches high.
https://www.containerstore.com/s/ide...=fridge%20bins