Ok, thanx to both of you. So now I get it, a resistor doesn't lower the amps it lowers the voltage. No, the resistor reduces the current (the Amps). The voltage is determined by the current through the LED as Styx wrote. So there's no need for a voltage regulator or lowerer (whatever) Correct
Now Styx mentions two in series. I'm going to need a few more than that (something like 20) so if each one needs 2.2v (maplins 3mm leds) then in theory I'd need a 44V power supply.... Is this right?????? No you can connect them in series parallel. Ignore the bicolour question for the moment. For single colour LEDs you would connect 4 is series with a resistor. 4 * 2.2 = 8.8 Volt. If you set the current to say 10 mA then the resistor would be (12 - 8.8 )/10 = 0.32 k. So use 330 Ohm. So for a total of 20 LEDs, you will need 5 strings of 4.
Also the LEDs are bi-color so how do I get the change in colour? You need to answer Ron's question before we can answer this one.