I've got a load of sure electronics RGB LEDs. They came with resistors, one value for the red pin and a lower value for the blue and green pins.
The red component looks quite a lot duller than the others. Is this normal, and to rectify it do I need to increase the resistance on the green and blue lines or is there something else I can do?
I have found the red is the lowest emitter followed by the blue and finally the green. So I would put the lowest resistor on the Red to give it more current.
I found that 220R on red 512R on blue and 910R on green gave me an acceptable white on the LEDs I had. Yours of course might be different.
Like Mike said, Red is just a dull looking color in general. A lot of the energy being put into the Red LED is wasted in colors that we can't even see such as infrared. To compensate, lower the resistance on the Red. You shouldn't need to increase the resistance on Blue and Green unless you have power consumption concerns.
-Austin 
Thanks both, I'll have a play with different values of resistors