Encountered a problem playing Youtube videos, which display wrong colors. This has something to do with Flash in Ubuntu. From Software Center, remove Flash. Then, open Firefox, go to Youtube and play a video. A pop-up will display of missing plug-ins, choose install. Here, instead of using Adobe's Flash plug-in, use the other, which is Gnash Flash plug-in (An open source equivalent of Adobe's Flash). Quit Firefox and launch it to watch videos.
Just found out from Ubuntu forums that you can fix this by playing a Youtube video, then click Fullscreen, right-click->Settings and disable hardware acceleration then refresh your browser.
That's it. enjoy!