After the American Revolution, the founding fathers seem to have adapted their 'costumes' from similar European ones. Like the Europeans, their uniforms often had orders, medallions and 'golden-like'-coloured-epaulet. But some of these symbols were only about civil respect, not about their military descent. So what about George Washington?
Washington conspicuously respected the subordination of military to civilian power as a general, and at his inaugurations and other official appearances as president, always wore civilian clothes. Still, that does not mean he never donned his uniform again. At least one surviving uniform is in the collection of the Smithsonian Institution, and to quote liberally:
This blue wool coat is part of a suit of regimentals made for George Washington in 1789. It has a buff wool rise and fall collar, buff cuffs and lapels, and buff lining; there is a row of yellow metal buttons on each lapel, as well as on each cuff.
This uniform was worn by George Washington from 1789 until his death in 1799; the small clothes or breeches and waistcoat, date from the revolutionary period.
In December 1798, Washington was recorded wearing this uniform when he visited Philadelphia on Provisional Army duty. He wore a similar uniform when he was commissioned by the Continental Congress as Commander-in-Chief of the Continental Army.
Lansdowne's iconic painting of Washington in civilian dress was not produced until 1796.
There are some sources which say he donned his Revolutionary War uniform when reviewing troops suppressing the Whiskey Rebellion, which Joseph Ellis writes is the last time a sitting U.S. president commanded troops in the field. Washington was not charging into battle at the head of the army, however, and I did not turn up any authoritative sources which mention his dress.
George Washington made a point of NOT wearing a military uniform in civilian life. In his First Inaugural speech, he pointedly wore a "cloth coat" to set an example for other citizens of the fledgling Republic.