I think what you are seeing is a video that originated on youtube that had nfusz interactivity overlay when it plays. They could have made it any color.

You can now play a nFusz video seamlessly within Twitter and Facebook. That is a big deal vs. publishing a link on those social giants and being whisked away to another site for a video with interactivity.

Will nFusz video's play natively in youtube one day? I don't think it matters but that would be great as well.

Keep in mind the video and interactivity works on other sites. Not easy vs. a static video with hard coded interactivity on a web page the coder controls.