fungus:
Hinjeniero:
The seller has answered, seems to be an expert about his products.Doesn't really matter...
The day they arrive you can just connect a low voltage across them and find out which way lights them up. The only difference it will make is the type of transistor you need.
Unfortunately, it also affects the circuitry needed. Common anode LEDs needing more than 5V can be controlled form the Arduino just with a N-channel mosfet or NPN transistor. Common cathode LEDs needing more than 5V require a P-channel mosfet or PNP transistor plus a level shift circuit, unless your 36V power supply has a floating output.