I store my scraps of cardstock by color. I often pull out many different color scraps (and make a big mess) when trying to work thru what colors I want to use on a project. I hate to clean up so its no fun to put all those scraps away properly.
The solution: I have a little plastic bag that I have a sample of each color of cardstock in. I write the name of the color on the cardstock to ensure I remember what it is. When I am working on a project, I can just pour the package out. I can pull out several colors and see what works best, and then I can quickly scoop all the samples up and put them right back in the bag.
I have also found several color combos that I wouldn't have thought of if they didn't end up next to each other in my sample pack.
The little sample pack of cardstock started waaaaaay back when I first started stamping. I didn't have the budget at that time to buy all the cardstock at once and I wasn't sure what colors I liked so I bought a litle sample pack off of ebay. I have added to this pack as new colors have come out. I used to carry this little pack to the store when shopping to help me match dp and accessories also.