LED's aren't usually 12V there is a current limiting resistor that is already built onto that board and the traces that supply power to the LED. Just find out what the package size is and use one (want to say it's a 1210). The problem is going to be matching the color. They are measured in nM wavelength, though they may have a color assigned to them as well. It's kind of like a Daylight or warm color florescent bulb, there are subtle differences in color. If you are changing color then just pick the one you want. Remember that they are diodes so if you connect them backwards they will not work unless you buy bidirectional ones which have 2 LED's built in.
Jeff
