Thanks a lot for confirming it @afre , at least now i am sure it’s not only something on my end 
Well the easiest solution is to pick twice the colors rather than collecting and entering them manually, bit tedious with filters like Customize Clut when you want to change a bunch of colors but there is no other choice for now.
Hopefully someone will find out what is wrong with the color picker and find a way to fix this one of those days.
Don’t know if this problem was present before the QT’s versions of G’mic, if someone still have a non-QT based version installed and can give it a try…
Thanks again for the help.