Hi Decepticon,
not sure if this answers your question but often what I do in post processing (Photoshop) is to place a few "color sampler" points on stars known to be white.
The adjusting levels in RGB channels to ensure they all reach 255 in the "info" window. Careful not to adjust past the 255 because you could push past it but it doest report past 255 (trick is go to 255, notch it back to 254 then gently nudge it back to 255)
Too aggressively stretching the high range of the histogram can result in bloated and colourless stars.. You could stretch the lower end of the data whilst trying to maintain star colour in the image, or you could open the image twice, stretch one image to get the desired image brightness in your target, then copy the stars out of the unprocessed image, layer them in on top of the processed image stretch them a little bit to brighten them up a bit, boost the saturation a little bit then adjust that layers opacity to taste..
If the stars are all white in your unprocessed image, then try taking some shorter exposures to record the star colours, then using the same method I mentioned above, layer the shorter exposures stars onto the processed image and adjust to taste...
