George Washington receiving a salute on the Field of Trenton,
featuring Blueskin, by John Faed .
“Blueskin was a gray horse ridden by George Washington. He was one of Washington’s two primary mounts during the American Revolutionary War. The horse was a half-Arabian, sired by the stallion Ranger, also known as Lindsay’s Arabian, said to have been obtained from the Sultan of Morocco. Blueskin was a gift to Washington from Colonel Benjamin Tasker Dulany … Dulany married Elizabeth French, a ward of Washington’s, who gave her away at her wedding to Dulany on 10 Feb 1773. [see conflicting information in a note at the bottom of this post]
“Blueskin, due to his white hair coat, was the horse most often portrayed in artwork depicting Washington on a horse. Washington’s other primary riding horse was Nelson, a chestnut gelding said to be calmer under fire than Blueskin. Both horses were retired after the Revolutionary War. Blueskin lived at Mount Vernon, until he was returned to Mrs. Dulany in Nov 1785 with the following note:” 
George Washington letter to Elizabeth French Dulany, 23 Nov 1785 .
General Washington presents his best respects to Mrs Dulany with the horse blueskin; which he wishes was better worth her acceptance.
Marks of antiquity have supplied the place of those beauties with which this horse abounded—in his better days. Nothing but the recollection of which, & of his having been the favourite of Mr Dulany in the days of his Court ship, can reconcile her to the meagre appearance he now makes.
Mrs Washington presents here Compliments and thanks to Mrs Dulany for the Roots of Scarcity.
Friday—past 2 ’Oclock
Mrs. Dulany” 
Benjamin Dulany was a friend of John Parker Custis (Martha Custis Washington’s son, George Washington’s step-son), and was a frequent visitor at Mount Vernon when he was courting Elizabeth French in 1772-1773. The Frenchs lived nearby. Benjamin and Elizabeth married in 1773, and some of the wedding party stayed at Mount Vernon. [2, 3, 4]
Washington made Benjamin one of his aides during the Revolutionary War.
Elizabeth French is the daughter of Penelope Manley, and the niece of Harrison Manley. The Manleys had business dealings with Washington. We will explore this in a future post.
Elizabeth French (1754-1822) is 1st cousin 8x removed of MKS in the Spratlin branch.
COL Benjamin Tasker Dulany (1752-1818) is husband of 1st cousin 8x removed Elizabeth French.
Regarding the statement above that Elizabeth was a ward of Washington, Margaret Amundson verified Elizabeth was a ward of George Mason instead.  George Mason is renowned for his authorship of the Virginia Declaration of Rights, and the Virginia Bill of Rights and Constitution.
 Wikipedia, “Blueskin (horse).”
 French Family Association.
 From George Washington to Elizabeth French Dulany, 23 Nov 1785.
 Where, how, or with whom, my time is Spent [February 1773] by George Washington.
 French Family Association, see discussion of Margaret Amundson.