Hi Paolo,
Is this broadband data, it looks more like you used a narrow-band filter is that correct? If so, you can't really calibrate using the star color tool. That requires broadband data.
I use l-enhance and i confirm @vincent-mod's words: it's difficult to obtain a good color star calibration. But i managed it to work sometimes with l-enhance, even if i have to tweak parameters for 20 minutes in an opposite way as mabula explained in that tutorial...
Sorry I had not seen the update of the post. But I never quite understand how to fix colors.
I use the L-Enhance filter
So it's clear to you now or do you still need further assistance, happy to help..
For narrow-band data, it's not possible to perform color calibration automatically. This is because APP uses the broadband data belonging to stars in their main phase of life. So you would need similar broadband data for it to work. Narrow band data is more down to the photographer on how to show this. You can use the real look of H-alpha for instance which is more pink, but many prefer red for instance.
Ok thanks 🙂