In 1902 there were undertaken at the Iowa Agricultural Experiment Station some investigations of the merits of "blue-gray" cross··bred cattle as feeding and market animals. The "blue-gray" color is caused by an intimate intermingling of black and white hairs on the body, a condition seen in cattle, horses and (rarely) in swine, and referred to by stock breeders as "blue·roan." The blue-gray color is not typical for any recognized breed of cattle and is most commonly produced by crossing a white Shorthorn bull on cows of the black Scotch breeds, namely the Aberdeen Angus or the Galloway-usually the latter.
Lloyd-Jones, Orren and Evvard, John M.
"Inheritance of color and horns in blue-gray cattle,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 3
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol3/iss30/1