Probably longer exposure may help to get the colour.
Have a look at my 1st (and only good) photo of the Sagittarius star cloud made with a tripod:
http://www.iceinspace.com.au/forum/s...ad.php?t=21306
50 x 10s exposures at ISO 800, 50mm f1.8 @ f3.8, the same camera as yours.
Regarding stacking RAWS, what I have noticed with Deepsky Stacker is that (Nikon) RAW files are "much darker" than JPGs, i.e. it will detect less stars in the RAW file (hence stacking goes quicker) and the resulting image will be darker. Set your camera to make RAW+JPG when taking photos and try stacking the same images in two formats and then compare the results. However, I am not sure adjusting the levels/curves afterwards will give a better image in the end with RAW.
Also here is a short guide how to play with levels/curves in photoshop written specifically with astrophotography in mind:
http://www.angelfire.com/space2/tgta...sing_part3.htm