The posters follow the other extra-canon media presented to boost demand and anticipation for the film. This includes websites and video propaganda as if it were made in-universe. Hunger Games has made excellent use of this through all four movies. The propaganda posters released by "The Capitol" for Mockingjay Part 1 were pretty suit. This propaganda all shows Katniss in a red mockingjay battle suit.
Much of Mockingjay (1 and 2) has cold war themes, including the reliance on Propaganda both by the Rebellion and the Capitol. The posters reflect that. The Capitol has it's own propaganda as well.
She does not wear a Red suit at all in the on-screen material.