Hi @Andy_Astbury1, the documentation is quite out of shape in areas. We’re certainly aware… writing new documentation and accepting contributions from users will become easier if we move the system away from MediaWiki. (see An update on Rawpedia - #19 by Entropy512)
As for the color of the mask: it is hardcoded, but perhaps could be made user-editable at some point. I did not manage to deduce where the color is defined tbh… should be somewhere in here: RawTherapee/iplabregions.cc at dev · Beep6581/RawTherapee · GitHub