Many applications these days (such as Pages, Keynote, iWeb, and Microsoft Office) use OS X's built in Color Panel to allow users to select the color for their objects. At the bottom of this Color Panel is a place to store swatches of colors. This is very useful if you are creating multiple pages in iWeb, for example, and you want to keep the colors consistent.
But what if you want to work on the project on more then one computer? How do you transfer those swatches from one computer to the other? After digging around, I found that the swatches were stored in a preference file in your home folder:
~/Library/Colors/NSColorPanelSwatches.plist
Just copy this from one computer to the similar location in the other, and you have transfered your Color Panel swatches.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060607063851264