If I wish to compare a shade of red to a shade of green to see if they are right for each other, I can't put them side by side using the color card because they are too far away from each other.  Although I have a great number of the actual floss colors already, I don't have them all.  They are housed in 3 project boxes at the moment and I sometimes have many of the colors separated into a specific project I am working on. 
I put on my thinking cap and decided that the best way for me to compare colors would be to actually have all of the colors.  As there are 500 color in DMC, that is a lot of colors!  Luckily, I have over 300 of them already.  I also wanted to have a color swatch available to me at all times and not tucked away in a project.  I finally decided to make up small swatches of each color using the idea they have used in the DMC color card.  I went to my local Dollarama and purchased 3 flexible cutting mats and two small, compartmented project boxes.  Then I went to a craft store and purchased a new package of the DMC number stickers.  For the last little while I have been cutting these cutting mats into tiny rectangles that are 1/2" wide x 3/4" long.  Each rectangle gets a number and a length of that color wound onto it, as shown in the photo above.  It is a painstaking job but, I feel, very worth it in the end.  
With these small color swatches I can then very easily check my color compatibility from one place and not have to find all of my floss that could be scattered in several projects at one time.  I will still be using my DMC color card all of the time, but these little swatches will be invaluable to me for the final color choices I make when designing my rugs and other projects.
When I explained the idea to my mother she immediately offered some of her DMC floss so that I may have a length of them to make up my swatches if she had a color that I don't have.  That saved me from buying 66 of the 194 colors I need to complete my set!  Each evening I have been winding a few of my colors onto the rectangles and making more rectangles as I need them.  I have made a list of the colors I still need and will pick them up whenever I see floss at a good price.  Of course this may take a while, but I am thrilled to have this underway and love the little swatches I have already made.