Re: Classic MPC C-3PO and R2-D2 uber detail build

There are resistor calculators online that will let you enter the colors and get the value.  I've got one on my phone. 

There are also charts.  A 'resistor value chart' search should get you something.  Generally, the LEDs themselves will all be in the 2-3v range using 20-25mA each.  Red is usually in the 2.2v range and cool white is in the 3.2v range with other colors mixed amongst those two relative extremes.  The resistor value comes into play when you have the circuit's voltage, in this case, 6v.  The resistor values will be relative to that, but wouldn't work on a 9v or 12v system.