1. How much current does the Light Stick draw?
(remmber to measure current with your multimeter in series, not parallel)
2. How much current can the GPIO pins provide?
Using 12V (yellow/black molex wires), the answer to #1 is
probably much larger than #2.
3. Will it light using 5v? (red/black molex wires)
4. How much current does it draw using 5v?
Even using 5v to power the light stick, the current draw is likely to be too high, but you might as well check since you already bought it.
Scott