Hi Jared - thanks for the detailed explanation.
Good to know that I can save one shot colour images using SGP using Nikon .NEF format instead of what I was doing, which was using .FIT format.
You see, when I originally imported the .fit files produced by my Nikon (via SGP) into Pixinsight and told it to debayer (by checking the “CFA images” checkbox in the batch preprocessing script), Pixinsight refused and eventually gave an error. Only when I unchecked that box did PI proceed to completion, in which case, after integration, I ended up with a greyscale image with a kind of ‘dotty’/streaky vibe about it.
So this seems to suggest that even when I upgrade to a proper cooled OSC camera like as ZWO ASI071 I will still have to avoid .fit format because as you said " SGP does not output 3 channel (Red, Green Blue) FITs". That would mean saving in some sort of raw format that ZWO supports - I’m not sure what that would be till I buy that camera.
Seems strange that, in this day where OSC cameras are rising in popularity, that SGP by default seems to support a non bayered .fit file format = mono. Its like SGP workflow favours people using filters. I think what I have run into might be a common trap for new users with OSC/DSLR cameras and there should be some sort of warning in SGP that if they select .fit format for a DSLR that they are not going to get colour.