Any references/regulations for that, or is it pure fantasy, please?
Pure fantasy. & yet not so far off the mark...
Civil War 'Regulation' wool shirts were Domet flannel, varying from creamy to off white colour, soon dirty greyish.
That being said contractors woolen shirts were known in varied colours of grey, blue, and red. With millions purchased, & available, they were issued indiscriminately long after the war, as the QM Dept reported, until 1880.
the standard army issue was a grey shirt during the 1876 campaign, but many of the troopers in the field wore civilian clothes
Absolutely correct, The regulations of 1872 & 1874 specified a gray flannel shirt.
Yet 10,000 blue flannel "of wool not suitable for blouses" were made into collarless shirts & issued. This was repeated in 1877-78. These are significant numbers for a small frontier army.
However the
regulation shirt remained gray until 1881.
Citizens shirts, whether cotton, wool, linen, or some blend were widely available, & could be any hue, or pattern.
All were to be worn
UNDER the blue 4 (old) or 5 (new) button blouse, a sack coat.
Photos are known of soldiers with their blouses tucked into their trowsers, appearing as if they are in shirtsleeves.
The Hollywood Cavalry Trooper in "Dirtyshirt Blue" is, by regulation, just that,
HOLLYWOOD.
Still, frontier & campaign dress tended toward casual & comfortable, rather than parade ground uniformity.
Interestingly the regulations specified that if the troopers were on duty in a 'Summer uniform'
of blue blouse, white (canvas) pants and straw hats, they were required to buy those articles out of their pay.
Their officers were enjoined to "in like manner conform"
& let's remember that lots more fighting, & many more campaigns, went on long after Custer's self-inflicted debacle.
Valerik
"Brave Rifles!!"
EDIT Grammar Police Warrant