So you have some skeins of floss (or yarn or beads....). You might want to list which colors you have (there's an iApp for that: XStitcher); you might want to be able to look at the colors you have and decide if you need another, mintier, green. You might want to get a palette from ColourLover
and match your craft material to it. You might want a set of Perfectly Christmas or Deep Forest or Slightly Gray But Not Too Depressed, Really, and you might want to go back to it some time later.
Either a photographic one or a sample card made of the real substance (except for the beads, which you would have to set in epoxy or something) can be helpful.
This arrangement of DMC colors is at least 25 years old, incomplete, and not in any order that makes sense to me, but I still use it to match unlabelled skeins and to loo over a bunch of colors quickly.