Yeah so long as you're shooting raws, the colour balance setting is irrelevant and you'll have to balance it in processing.
I've recently began tackling this using an inexact and crude method, but basically I pick a dark patch on the image to set the grey point and it gets it in the ball park. The red histogram might need dragging down a bit still, but you'll be able to see that. Yellow stars become yellow again and blue stars become blueish.
I looked at the challenge of calibrating using G2V stars and my skills aren't up to it yet
The grey card is another method I read about, but I haven't tried getting hold of one. It seems it would give you a fairly accurate profile for correcting whatever images you take.
Ultimately though you are going to end up with a lot more red signal in your images because the camera has opened its eyes to it. I've only tried a few test shots on obvious nebulous areas and was really surprised at how quickly it captures the nebulosity, hope the weather cheers up a bit so I can start capturing some real data soon.