For those who have the time to do their own case dyeing it can be done with Rit Dye. The red is Cardinal Red, Blue is Royal Blue and Yellow is Golden yellow. The ones from Slots are a combo of Pink and Fusha.
The trick is not to melt the cases while dyeing them. The 43mm Airtites with the foam ring hold up the best under heat. The direct fits seem to be the biggest problem with melting.
If you don't want to go to all this trouble, Bill Cohenour's idea with the permenant marker on the edges works the best. If you store in racks you can spot the colors right away.
Here's an example of the dyed ones next to the originals. Any questions on the "how to" email me.
Jeff