DeepSkyStacker .Fits Options - bayer pattern selection

To de-bayer a FITS image first make sure to check the box "Monochrome 16bit FITS files are..."

If we select a different bayer pattern option and click "Apply" it will update the view of your sub file (unless your viewing an "output" file) which should always be green (in empty sky areas) and it appears more green when we "stretch" the view's histogram by bringing the black and grey triangles (below the black to white gradient bar that's above words "RAW/FITS digital development..." in this image) closer together.

Two of the top four choices (for simple 2x2 RGGB bayer patterns) will show greenish sky and two will look violet. One of the two green ones may incorrectly have the red and blue colors reversed in your output picture so select the other and re-stack if that's the case.