I think what you are referring to is the Lime Green Mickey Head Paint Chips (LGMHPC) from Home Depot. Disney makes a paint line that Home Depot carries and the DISers adopted the "Alien Green" (lime green) color as their signature color. There is a thread called "our secret green club" somewhere on here (I can't find the link to post it). More info is there for you. Its turned into a little competition to go to your local HD and swipe as many as you can and display them when you are at the World so other DISers can find you and possibly come say hi. Hope this helps. There are lots of threads on this board explaining it more in depth. This is the short version.
Happy Planning!