The red coloration of the bearded vulture is cosmetically acquired by bathing in iron-rich spring water and can vary in shade.
Adult bearded vultures are a dark gray-black or gray-blue in color, with a slightly darker tail and lighter shaft-streaks. Each side of the face is separated by a thick black band around the eyes, with long, broad black bristles at the base of the bill that resemble a beard. The forehead is a creamy-white, yellow color, while the rest of the head is a maize color, often becoming more of a rusty red-orange rufous color on the neck and abdomen that is darker on the throat and neck. The face is variably black-streaked with black ear-tufts. The chest is speckled with black streaks and broken spots.
The rufous coloration of the bearded vulture is not natural, but instead cosmetic. This orange color is acquired by dusting or bathing in iron-rich spring water and varies in shade depending on the amount of time an individual baths. The red color can be washed or brushed off to reveal natural white feathers.
Sources: (Ferguson-Lees & Christie, 2001; Tenenzapf, 2011)