To create the desired look, the filmmakers turned to visual effects supervisor Christopher Townsend, who previously assembled the de-aging looks for the earlier Avengers movies, alongside artists at the visual effects house Lola to transform Jackson and Gregg into what their characters might have looked like in the mid-’90s.

https://www.forbes.com/sites/adawson/2019/02/27/samuel-l-jackson-and-clark-gregg-de-aged-in-captain-marvel/#64002200487b