Dotty...I do the same thing.... There are a lot of foundation paper piecing blocks, too, so I set “waste” of background clippings in a plastic bag and use those pieces as much as possible for PP blocks. I think most blocks are using pieces 3 1/4 or less so I’ve been using that size when cutting strips from fabric, as well.
Toverly....great idea on poster board. You can also use the grid provided and use crayons or colored pens etc. to identify all the block colors. I did that with just one color because I don’t have much of it and I’m assembling as I go so I can’t swap them out later.