Julia Roberts, Gwyneth Paltrow, and Hilary Swank will soon be handing over their Instagram pages to black writers, businesswomen, and activists as part of a new social media campaign.On Wednesday, for one day only, a host of white women with large online followings, including the Hollywood stars, will use their platforms to amplify the work of black women they are partnering with as part of the #ShareTheMicNow initiative.