Ooooh... purple! Where's Mike?
OK, let's start with the basics. You've got what appears to be very decent data. Here's a "get a quick image" process. I'm going to ignore the Ha for now, and just work with the RGB. Let's get that data processed... then we can play with luminance and Ha enhancements. Note, the process I'm about to lay out is _NOT_ how I would approach and edit this data for a final presentation. This will be a quick and dirty method to give you an idea of how your data looks when built into an image.
Step 1: combine your R, G and B channels using the ChannelCombination process. To everyone who is furiously smashing their keyboards typing responses to the effect of "that's absurd, why are you combining the channels as step 1???" I ask you to read the previous paragraph again. I'm just laying out the process to turn Bill's data into a less purple version.
Step 2: Crop. With dithering (you _were_ dithering, right?) and setting up / tearing down and plate solving tolerances and more, you're going to have stacking artifacts that need to be removed. I can't tell you how much you'll need to crop, but I typically start at around 98% and work down from there.
Step 3: DynamicBackgroundExtraction. Lay out your samples in areas outside of M31, M110, etc. Ensure you've got good coverage and a decent tolerance. Trial and error here until you get a good model. Use subtraction, not division.
Step 4: PhotometricColorCalibration. Use the default settings. Put in the coordinates / pixel size / focal length... all should be filled in automatically by clicking the "Acquire from Image" button.
Step 5: ScreenTransferFunction to do an unlinked auto-stretch
Step 6: HistogramTransformation. Drag the blue triangle from the ScreenTransferFunction to the bottom of the HistogramTransformation process, then drag the blue triangle from the HistogramTransformation process to your image.
That's it. At this point you should have an image that is (hopefully) not purple.