Thank you very much guys!!
I know FCPX is not a good tool for colour grading, but if the Apple engineers decided to add this feature, FCPX will grow. With something like this colour grade will be an option in FCPX. Yes I know, Davinci or others always be better option, but sometimes we only need a basic colour grade.
AFX have this option via expressions, and is really useful.
All the best
Juan