Lighting LED Power Supply

Question: How long would you need to run the LEDs? Batteries will power them for quite a while as they draw low power but other than that, model train transformers put out around 12V, but you will still will need a "dropping" resistor to further reduce the voltage. 470 Ohm resisters are what I used on my model train layout, but I would do a bit research if I were you. A good model train shop, if you have one available, would have some great advice.

You can't run multi-color LED's off of just a transformer as it just puts out a lower voltage of AC current and multi-color LED's must have DC current available to get all of the colors.  I am assuming you have red-yellow-green LED's in which case green is established by a negative DC bias, red with a positive DC bias and yellow with AC.  At minimum you will need a 5-6 volt transformer, full wave diode bridge, variable voltage regulator(with control circuitry) and three position double pole selector switch.

There are thousands of circuits avaiable online that will do the job and  many have automatic switching features to go between the colors in the pattern of your choosing.  A good place to start is Popular Electronics' web site.  HTH

                                                                                    Pat