Why women are posting black-and-white photos with the caption 'challenge accepted'

Celebrities and Instagram users are posting black-and-white images in support of women's empowerment with the caption "Challenge accepted."

(CNN)Instagram has been overrun with women, famous and otherwise, posting black-and-white images of themselves with the caption, "Challenge accepted."

There doesn't seem to be much motivation for the photo challenge. That may be by design.
Celebrities like Gabrielle Union, Kristen Bell and Kerry Washington have accepted the "challenge," which seems to involve posting a black-and-white image of oneself as a show of women's empowerment. There's no obvious social justice bent here other than to encourage women to share photos of themselves where they feel confident.
    It works like this: Women nominate each other to post a monochrome image of themselves that they presumptively like. They share their photo, usually with the caption "Challenge accepted" and the hashtag #womensupportingwomen, and tag other women to post their own.
    It's reminiscent of the Dolly Parton challenge, which encouraged users to post four different images of themselves that they'd use as hypothetical headshots for different social media sites like LinkedIn and Tinder (a studious photo for LinkedIn; a sultrier shot for Tinder). That mostly functioned as a vehicle for users to post four flattering photos of themselves at once.
    Ava Duvernay touched on that in her "challenge accepted" post. The "Selma" director shared a striking-black-and-white headshot and said she was "pretty sure this is just a cool excuse to post pix," but she relented at her friends' behest.