It's been just over a year since Google first started publicly testing a new Material Design makeover for the YouTube website. The design has gradually rolled out to some users, but many (myself included) had yet to get it officially. Now YouTube is allowing anyone to try it out.
In a post on the YouTube Blog, the company explained that the new design uses Google's Polymer framework. One of the advantages to switching to Polymer is a new dark theme, which you can enable by clicking your user icon at the top-right and selecting the Dark theme menu option. Overall, I quite like the design - but I do wish there was more color.
You can try out the new design by visiting youtube.com/new. If you don't like it, you can go back by clicking your user icon and selecting 'Restore classic YouTube.'
- YouTube Blog