I sometimes struggle with the sorting of fabrics.
What I found that works best for ME is to look at the background
color, is it predominate over any other color? if yes then I put it into
that pile (predominately black background goes into the black pile etc.).
If there is a variety of colors in equal or close to equal amounts then
I put it with a "multi-color" pile, you would be surprised at how much
fabric I have in this pile.
Of course this might end up changing as I get going more with sorting
fabrics to share with my daughter who is beginning quilting. She doesn't
need to go to a fabric store to buy. All she has to do is go shopping at
"moms" place.
LOL