An excellent reference for French infantry of the period is Rene Chartrand's The French Army in the American War of Independence.
The French Army was in the middle of a significant reform period ca 1763-1789. In 1776 all infantry regiments were ordered to have two battalions each. The senior infantry regiments that had four, had their 2d and 4th Battalions reformed as new regiments.
Battalions were reorganized to have six companies instead of nine-one grenadier, one of the newly-created chasseurs, and four fusiliers.
The Regiment Agenois was formed from the Regiment Bearn.
The Agenois uniform by the 1776 Dress Regulations had pink lapels and cuffs, a green collar, and white metal buttons.
The 1779 Dress Regulations had the Agenois with white lapels, violet cuffs, and yellow metal buttons. White lapels were edged with piping in the facing color. The collar was white piped in the facing color. Shoulder straps were white piped with the facing color for fusiliers. Chasseurs had green shoulder straps piped white, and grenadiers red piped white. Grenadiers in many of the regiments retained the red fringed epaulets.
Clothing was issued to one-third of the regiment per year so that in a three-year period, the entire unit would have the new uniform.
Some leeway should be given as to the implementation of the new regulations.
From page 34 of the reference:
"Officers were to wear the same uniform as their men but made of finer material with gilded or silvered buttons. Rank was distinguished by a complex system of epaulettes in gold or silver, with captains and subalterns having (in scarlet for the metropolitan army, in facing color for colonial troops) silk lines and diamonds on the straps. The sword knot for all officers was gold, mixed with silk of scarlet for the metropolitan army, facing color for colonial troops, for captains and subalterns. When on duty, officers wore a gilt gorget with a silver badge bearing the arms of the king at the center."
The 1776 Regulations specified a uniform cut in the Prussian style which was tight and unpopular. The 1779 Regulations changed that to a more roomy and comfortable uniform which was much more popular. The 1779 Regulations specified a stand-up collar.
