If you simply want them on when you plug them in, then yes, it's pretty easy to do. If you want something controller by CH3 or something, that gets more difficult.
They should go on, when I plug them. Are there any white and red lights available for 7.2V (6 cells). I think it is easier to purchase them instead of building this on my own.
Hmm, not sure if there are any wired up pre-made for 6 cells. Have you checked Tower for something like that?
However, it really is quite easy to make up your own. Just a resistor in series with each LED is all it takes, which would be perfect for 5v or 6v. There are formulas and such if you're interested in building your own, just let me know if you are interested.