Steve Rogers seems to have made some serious alterations to his Captain America costume. It appears to have been made darker, now fully black rather than a navy blue, but it is still clearly Captain America’s costume because the stitch-marks where the bright white star used to be can still be seen, though the star itself has apparently been removed.
Those who have noticed this change have gone about referring to Steve Rogers now as Nomad, referring to an era in Steve Rogers’ Marvel Comics history where, after discovering that the president of the United States was a member of the Secret Empire, Rogers became disillusioned with his nation and left the persona of Captain America behind to become he Nomad, the man without a country.
However, we think there’s a more apt persona from a different period in Captain America’s history that has more in common with what appears to be going on with Steve Rogers in Avengers: Infinity War. It is The Captain from the Mark Gruenwald “Cap No More” storyline from the late 1980s...Steve Rogers' The Captain costume bears a striking similarity to the one Steve Rogers is wearing in the Avengers: Infinity War footage. The most obvious similarity is the color.
Both Roger's The Captain costume and the one from Avengers: Infinity War are black (or at least the live-action appears black on the Comic-Con poster).