Is the lack of star colour due to saturation? Hover over the stars in one of the original sampled subs and check. If many of them are saturated it might be hard to get colour? I've just started on the Trifid and had to drop the exposure time compared to some other targets I've been doing.
Star masks, now you're on the slippery slope to ... Range masks, range-star masks ... A few interesting variations on star masks that I've tried. The second is a doozy!
https://www.cloudynights.com/topic/6...good-starmask/
https://pixinsight.com/forum/index.php?topic=11879.0
And there's also starnet which has now be made into a pixinsight process. But at present it can only be used on non-linear stretched images
Edit: Gavin I just looked at an autostretched version of the M20 I've started on (only have 2.5hours so far). The bigger stars on mine are very white/blue, only the smaller ones have much colour. You might have a look at the Trifid war over on the other forum - the big stars on many of them also look white/blue