The fluorescent paint actually consists of several substances. First, there is the fluorescent chemical, which does not give off any color under normal light but glows under ultraviolet light. This chemical is different for each color of paint. Then, there is the transparent dye that gives off the color under normal light, but doesn't glow. Distinguishing between fluorescence and phosfluorescence is also important.
Phosfluorescent materials continue to glow after the light source is removed.
These are what we call glow in the dark materials. In case you're wondering what ultraviolet light was used for before the Hippie thing happened, it has many uses. First of all, I need to point out that there are two kinds - long wave and short wave. The long wave lamps were the ones that Hippies use and are generally considered harmless. The short wave lamps are the ones that can harm you.