Google really likes icons that are just contours. After the multicolored makeover of all Google service app icons, it changed the YouTube interface and replaced the standard look with line art. Now the shift has come to the desktop / web version of YouTube. So yes, that’s one thing.
The revised icons appeared in the menu on the left of YouTube today ̵
Old icons on the left, new on the right. Slide to see the difference.
The new YouTube icons follow some of the interface changes made to other Google services, such as Gmail and Messaging. The reaction from users has generally been negative, and some complain that the new icons are more difficult to distinguish.