They are not digital photos, but from films. Color films require 4 layers for colors. B&W has only one metalic silver layer and because there are no colors, it can be more granulated. I think, that silver crystals were even smaller than what was from color layer crystals, so B&W films had not 4x times more silver "pixels" but even more, compared to what color films had, hence the reason why those color pictures look so blury, compared to so good B&W pictures.
Not to mention, that B&W films and pictures with very good results could develop every amateur and during the development process add various effects - sepia is one of them, but you could get blue tint by mixing some other chemicals.