Bob, LEDs don't have a voltage rating as such, instead a series resistor is used to limit the current to a suitable value. A typical modern ultra-bright LED of any colour will have a maximum current of about 20mA therefore a 1.2 Kohm resitor (Maplin stock number M1K2) in series will allow use up to 24V but will still give good brightness at much lower voltages down to the minimum likely to be encountered. The actual voltage dropped accross the LED at its rated current will be about 2V for red/green/yellow and about 3.3V for blue and white types however they should not be connected directy to these voltages. Take care to ensure the LED is the right way round otherwise it may be damaged, the shortest lead going to the negative supply and the longer lead via the resistor to positive.
It is possible that the controller already has a resistor in series with the led supply but this will not cause a problem, just a small reduction in brightness.
