Do you think he just looked at Shuri and said, deadpan… Blue.
Like any good nerd, I think that Shuri did her research (after posting a few embarassing videos of T’Challa of course). When it came time to design something for ‘Bucky’ to wear, she began by looking at what he’s worn in the past. Until proven otherwise, I’m giving her full credit for combining elements from each of his uniforms to create something new because it feels completely in-character.