The 800 "marines" serving in the siege force at Gloucester Point opposite Yorktown in 1781 were not really infanterie de marine. Although the Minister de la Marine had tried to establish 100 companies of a "Corps Royal d'Infanterie de Marine" since 1774, he had not been too successful by 1779. So the French Royal Navy was forced to continue stationing detachments of soldiers of the army on the ships of the fleet, as had been the custom since Louis the XVI's time.
So the 800 marines were actually soldiers of 10 army regiments being despatched from 14 ships of De Grasse's fleet.
They were 75 soldiers and 3 officers of the règiment de Picardie, 30 soldiers and two officers from the Provence regiment, 75 men and two officers from régiment de Brie, 40 and a capitaine from de Bresse, 150 and 4 officers from Du Maine, 30 and 1 capitaine from La Sarre, 30 and 1 officer from Bourbon, 75 and 2 officers from Monsieur, 190 and 6 officers from Angoumois, and another 30 and 1 lieutenant from Rohan-Soubise. They wore their normal white uniforms with differentiating facings.
(I adopted some Wikipedia uniform schemes here to illustrate the differentiating facings.)
In the beginning of the siege there had been only 1200 Virginia militiamen under the command of General George Weedon on the left bank of York River to block a possible escape of general Cornwallis from Yorktown. This was not a really reliable force, and its numbers varied daily! After the cavalry and infantry of the Duc de Lauzun had arrived, it was thought necessary by the Allied command to have further troops there to strengthen the position. So Admiral De Grasse was "persuaded" to delegate 800 men and 23 officers of infantry from his fleet - which he reluctantly did. The command of the entire force at Gloucester was given to the French General De Choisy.
I have made up my "800 marines" of 40 infantry figures by Front Rank and Foundry, adding a few officers, one of which is by Dixon.
As postures I decided on halting, firing and at the ready types, because their main objective was to block any attempts by the commanding British general at Gloucester, Banister Tarleton, to go out foraging.
I was glad having added 10 French regiments to my forces in this way!