No they are not, a LED is a current dependent device, there is a voltage across them, 1.2 volt for red, and 3 volt for white, but it is current that matters, so some where some how a driver is included, this may be a simple resistor, or capacitor, or a complex switch mode device. To make a decoration a simple resistor is often used, so three LED's and a resistor from a 12 volt supply is very common, but where used to light an area the resistor is very wasteful so a switch mode driver is used, so voltage or current you find out by reading the instructions. There is no standard.Thanks Winston.
In principle though, is cool white sound?
Are they all 12v dc, or are they not?