I now get a green display only on videos in youtube and facebook, although I do get sound. Is this something to do with the latest update which I see was on Thursday?
Sorry for my reply. I am only an F-Secure user (their home solutions).
Maybe it is good to know a bit more information about your setting. For examples, what is your device / OS? And what is your F-Secure solution? Is it Windows / Mac / Android? And is it about F-Secure SAFE? If it is Android platform - then is it about F-Secure SAFE browser?
In addition, the latest update is for F-Secure solution? Or some third-party (for F-Secure software) things like Adobe Flash Player or so?
In general, Google Support pages have the next article: Green screen in video player - YouTube Help (google.com)
where some steps to fix a trouble are placed.