New Avengers: Endgame concept art gives Tony Stark and Captain America a different set of time suits.
The film utilized time travel to help the Avengers undo Thanos' dusting of half the universe, using Quantum Realm time travel suits. Ryan Meinerding, Head of Visual Development at Marvel Studios, posted to his Instagram one alternate take on the time suits.
The Avengers' time travel suits were predominantly white with slivers of red in different areas. Meinerding's post portrays Captain America and Tony Stark's suits as dark-colored while retaining their original design. The suits look like a mix between dark gray and black. There is still red within some regions of the costumes, such as the Avengers logo on the arm muscles.
The time travel suits help the Avengers traverse the Quantum Realm to grab the Infinity Stones from different past events. They were designed by Stark using inspiration from Hank Pym's work and used nanotechnology to make them easier to put on. With time travel now officially part of the MCU, future installments could make use of it. It is unclear if the Quantum Realm will be used again for this mechanic.
Avengers: Endgame marks the end of an era as the Avengers fight to bring back all they lost at Thanos' hands. The film stars Chris Evans, Robert Downey Jr., Scarlett Johansson, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Bradley Cooper, Brie Larson, Paul Rudd, Karen Gillan and Don Cheadle, along with other numerous stars.