Jeff Liebermann wrote:

(...)

At least the perpetrator and the exact location of the
collision will be easily identifiable.
http://www.paintballimpact.com/special-effects/booby-traps.html
http://www.zdspb.com/tech/misc/paintballcomposition.html

Cool!

Fluorescent dye that shows up only under ultraviolet
would work nicely.
Perhaps a two-part paintball with visible and
invisible paint?

--Winston