This is the Uniform of George Washington.
Consisting of coat, waistcoat, and knee breeches, he wore it from 1789 until his death in 1799.
He wore it when he inspected the troops called up for the Whiskey Rebellion in 1794.
He also wears it in John Trumbull’s famous 1790 painting of him at Verplanck’s point.
Washington devised the blue and buff colors of the uniform while serving at the Second Continental Congress in 1775, just prior to being named Commander-in-Chief of the Continental Army.
In honor of this, the U.S. Army would use the same color scheme up until the start of the civil war.