is the new...

(something) is the new (something)

Something has replaced something else as the most fashionable, trendy thing of the moment. In the office of this young billionaire, jeans and a T-shirt are the new business casual. Trust me, navy blue is the new black when it comes to winter jackets.
See also: new

... is the new ...

(British English, informal) used to say that something has become very fashionable and can be thought of as replacing something else: Brown is the new black.Comedy is the new rock and roll.Fifty is the new forty.