I friendly yard dog saw one of my projects and gave me some good advice about painting Kydex (Thanks Myke).
He inspired me to do a little more research and I came across the big enchilada of Kydex info on none other than Kydex.com. If you ever want to experiment, it might be a good idea to mark this page.
You never know when you are going to need to know what the effects of Cobalt-60 gamma radiation at energies of 1.173 MeV to 1.331 MeV will have on the color of your sheath.
Don't worry, there is actually some useful stuff here too.
http://www.kydex.com/technical-data/technical-briefs.aspx