Thanks for the correction DC! It's an important point.
We're talking about UV dyes. They are most often used for leak detection.
Dye-lite is a brand name of such a product. It is available in green for a water based application, and in yellow for oil based. It is also available under the name Fluoro-lite, for refrigerant leak detection (i.e. your car's air conditioner).
Here's where it comes from:
http://www.tracerline.com/assortment_packs.html
These guys have it in Green and Blue:
http://www.spectroline.com/hvac_fluo...uel_water.html
Blue: WD-801
Green: WD-802
Check this for a lamp:
http://www.tracerline.com/lamps.html