The Blue variety of Orpington was accepted into the APA Standard in 1923. The creation of the blue variety has been credited to William Cook's daughter, Elizabeth Jane. After her father's death in 1904, she bought out her brothers' and sister's shares of the Family Business. She continued her father’s work under the banner of William Cook and Sons. In 1907, she released the Cuckoo Orpington and the Blue Orpington. In 1911, she introduced the Red Orpington.
The Blue Orpington is bred to the same Standard as the Black.
The Blue Color
Male plumage: Hackles, saddle, wing bow, back and tail dark slate blue. Remainder medium slate blue, each feather to show lacing of darker shade as on back.
Female plumage: Medium slate blue, laced with darker shade all through. The head and neck, dark slate blue.
In both sexes: Beak black. Eyes black or very dark brown, black preferred. Comb, face, wattles and ear-lobes bright red. Legs and feet black or blue. Toe-nails and bottoms of feet, white.
per the UK Standard
Andalusian Blue is caused by a "modifying gene", an autosomal, incompletely dominant gene (Bl) that, when bred to a "pure" black bird, produces the desired "Andalusian Blue" only in the heterozygous form. A more simplified description is blue is a diluting gene. One copy dilutes Black to Blue. Two copies dilutes to Splash
In the Andalusian Blue, the ideal feathering is be an even shade of ashy, blue-gray throughout the bird, with each feather laced in a bluish black. The edges of the feathers are black all the way around with no shafting, stippling or mossiness in the centers. The Female bird will have darker head and hackles. The male bird will have a darker head, hackle, cape, and saddle.
The Andalusian blue gene, when homozygous , creates "Splash" or "Blue Splash" feathers. These birds are muddy or bluish white with occasional, randomly "splashed", black feathers.
Blue can come in varying shades even from the same parent birds. There are many other genes that effect the shade of blue as well as the quality of the edging. Blues without correct melanizers can appear very washed out in color to the point that they can be mistaken for lavender/Self-blue.
blue black splash breeding chart