I found a handy way to keep paint swatches. I paint a wood door hanger [found at any craft store for less than $1]. I like looking through the hole at the fabric to see how I feel it's going to work in a room. I feel having the ability to look at the color all the way around a fabric is really essential for me.
On the back of the door hanger, I write the paint information.
Here's another hanger which is my house's primary color. I have this color memorized, but wrote down which areas of the house were painted with this color.
Yea, it's pretty much everywhere.