Easiest project ever, but I still need straight answers. AA 1.5v x2 to RGB LED (trying to make white)
You need 3 batteries minimum, and 3 resistors. With 3 batteries, try 







simulate this circuit &ndash; Schematic created using CircuitLab
You have 2 problems. The really fundamental one is tieing the LEDs in parallel. They operate at different voltages. The red has the lowest voltage, and it's hogging the current from the others. You need a separate resistor for each LED. Red has the lowest voltage, green next, and blue the highest. The current (and brightness) is determined by the resistor, so for the same supply voltage you really ought to have different resistor values. This is not entirely true, since different LEDs can have different efficiencies, but it's a good starting point.

The other problem you have is using a 3 volt battery. This is just about the blue LED voltage. When you first connect the blue LED, the battery has just enough voltage to light the LED, but this quickly gets exhausted. When you disconnect the battery, it recovers and will briefly work again.