There are specialist OPAMPs with enough bandwidth for video, but its not easy even if you have RGB component video with seperate sync and the odds are it wont work well unless you only need a small boost, as its likely to overload the blue input of the monitor.
OTOH it should be possible to attenuate the R and G signals and turn up the brightness and contrast on the monitor to get a similar result.
RGB with sync on green would be quite a bit harder - you'd probably need a sync seperator then reinsert the sync after attenuating the green.
If you've actually got YPbPr video its a real mess of complex analog circuitry to do what you want: convert to RGB with separate sync, boost the blue then reconvert back to YPbPr.