Yes, this is legit. I searched the sources including M.A.C. press releases, Twitter tweets and reports by sites including Scary Mommy and Glamour.
You can get a FREE full-size M.A.C. lipstick on Saturday, July 29th for National Lipstick Day. Value usually is around $17. Where? Anywhere M.A.C. cosmetics are sold, which includes Macy’s and ULTA.