Many companies were formed before the state seceded and chose the uniform of their liking. For example the Westville Guards.
[Westville, Mississippi. September 18th, 1860
To His Excellency John P. Pettus
We the undersigned Citizens of Simpson County, have associated ourselves together for the purpose of forming a Volunteer Military Company in said County, and therefore pray your Excellency to grant an order for the election of officers for said company.
We have adopted Mississippi Rifles with bayonets for our arms and have adopted as our uniform dark blue with yellow buff trimmings, cap with red-topped pompoon, Name adopted "Westville Guards"...]
Photographs of two Mississippi soldiers, one specifically identified as a Westville Guard in July of 1862, the other wearing an exact copy uniform, are wearing a uniform different than the above discription, and are more in step with the State regs.
The Jeff Davis Rifles are photographed in Pensacola with cuffs and collar trims that looked to be black.
The state regulations for Army of Mississippi in early 1861 stated...
crimson for infantry and riflemen
yellow for cavalry
orange for artillery
On March 14, 1861 these regs were changed to...
green for infantry and light infantry
red for artillery
yellow or orange for cavalry
In May of 1861 the regs were changed again...
blue for infantry and riflemen
orange for cavalry
red for artillery
I know that I can date when a soldier from the Westville Guards changed his original company regulation frock coat for a new shell jacket after the Battle of Second Manassas in the late summer of 1862 when his company recieved a shipment of new clothing.
For those who wore red trim- it is being reported that these companies did at one time...
Lamar Rifles
Water Valley Rifle Guard
Ben Bullard Rifles
Mississippi Rifles
Pettus Rifles
Sunflower Dispersers
There are probably many more.
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David Upton