The 43rd Battalion were partisans who melted into the civilian population when not on a raid, and at one point General Grant ordered several captured partisans hanged for being out of uniform.
Nonetheless when raiding they did wear Confederate gray at least in some fashion.
Munson said in his memoirs:
"Something gray" was the one requisite of our dress and the cost of it mattered little.
Much of it was paid for by Uncle Sam out of the money we got from him directly and indirectly. . . .
It has been said that we wore blue to deceive the enemy, but this is ridiculous, for we were always in the enemy's country where a Southern soldier caught dressed in a blue uniform would have been treated to a swift court-martial and shot as a spy.
I never knew, nor did I ever hear, of any man in our Command wearing a blue uniform under any circumstances . . .
We had no reason to use a blue uniform as a disguise, for there was no occasion to do so.
Many of our attacks were made at night, when all colors looked alike, and in daytime we did not have to deceive the Yankees in order to get at them.

Munson's denial of the use of Union blue is contradicted by another source however.
 The diary of Union mapmaker Private Robert Knox Sneden, who Mosby captured near Brandy Station, Virginia at 3:00am November 27, 1863, records that Mosby's raiders were disguised in Union Blue overcoats, and so was Mosby himself.
 While interrogating Sneden, Mosby "opened his blue cavalry overcoat, showing a Rebel uniform underneath."

Mosby's men each carried two .44 Colt army revolvers worn in belt holsters, and some carried an extra pair stuck in their boot tops.
Mosby and his men had a "poor opinion" of cavalry sabres, and did not use them.
Munson "never actually saw blood drawn with a sabre but twice in our war, though I saw them flash by the thousand at Brandy Station."
Union cavalry initially armed with the traditional sabre fought at a considerable disadvantage:
The Federal cavalry generally fought with sabres; at any rate they carried them, and Mosby used to say they were as useless against a skillfully handled revolver as the wooden swords of harlequins.
As the Mosby tactics became better known, scouting parties from the Northern army began to develop an affection for the pistol, with increasing success I might add.
In stubborn fights I have seen the men on both sides sit on their restless horses and re-load their pistols under a galling fire.
This was not a custom, however; someone generally ran to cover after the revolvers were emptied.
 We both did this a good many times but, I believe, without bragging at the expense of truth, that we saw the back seams of the enemy's jackets oftener than they saw ours. . .
Revolvers in the hands of Mosby's men were as effective in surprise engagements as a whole line of light ordnance in the hands of the enemy.
This was largely because Mosby admonished his men never to fire a shot until the eyes of the other fellow were visible.
It was no uncommon thing for one of our men to gallop by a tree at full tilt, and put three bullets in its trunk in succession.
This sort of shooting left the enemy with a good many empty saddles after an engagement.

For instance, describing the fight at Miskel's barn, Munson says of William H. Chapman (later lieutenant colonel of Mosby's command) wheeling his horse in a thicket of Yankees "[t]he pistols were not a foot apart.
The Yankee's pistol snapped [misfired] but Chapman's did its deadly work.
He fired six shots and emptied five saddles."

A few guerrillas equipped themselves with carbines captured from the Union, but "they were unhandy things to carry" and unsuited for fighting on horseback; indeed in the thick of a February 1865 fight the carbines' long barrels made them too unwieldy to fire, and they were used instead as clubs.
Mosby tried out some small field artillery pieces, including a 12-pound (5.4 kg) brass Napoleon, but artillery proved to be too cumbersome for his fast hit-and-run tactics and not especially helpful in action.
Ultimately Union troops found the mountainside hiding
The 43rd Battalion were partisans who melted into the civilian population when not on a raid, and at one point General Grant ordered several captured partisans hanged for being out of uniform. Nonetheless when raiding they did wear Confederate gray at least in some fashion. Munson said in his memoirs:
"Something gray" was the one requisite of our dress and the cost of it mattered little. Much of it was paid for by Uncle Sam out of the money we got from him directly and indirectly. . . . It has been said that we wore blue to deceive the enemy, but this is ridiculous, for we were always in the enemy's country where a Southern soldier caught dressed in a blue uniform would have been treated to a swift court-martial and shot as a spy. I never knew, nor did I ever hear, of any man in our Command wearing a blue uniform under any circumstances . . . We had no reason to use a blue uniform as a disguise, for there was no occasion to do so. Many of our attacks were made at night, when all colors looked alike, and in daytime we did not have to deceive the Yankees in order to get at them.
Munson's denial of the use of Union blue is contradicted by another source however.  The diary of Union mapmaker Private Robert Knox Sneden, who Mosby captured near Brandy Station, Virginia at 3:00am November 27, 1863, records that Mosby's raiders were disguised in Union Blue overcoats, and so was Mosby himself.  While interrogating Sneden, Mosby "opened his blue cavalry overcoat, showing a Rebel uniform underneath."
Mosby's men each carried two .44 Colt army revolvers worn in belt holsters, and some carried an extra pair stuck in their boot tops. Mosby and his men had a "poor opinion" of cavalry sabres, and did not use them. Munson "never actually saw blood drawn with a sabre but twice in our war, though I saw them flash by the thousand at Brandy Station." Union cavalry initially armed with the traditional sabre fought at a considerable disadvantage:
The Federal cavalry generally fought with sabres; at any rate they carried them, and Mosby used to say they were as useless against a skillfully handled revolver as the wooden swords of harlequins. As the Mosby tactics became better known, scouting parties from the Northern army began to develop an affection for the pistol, with increasing success I might add. In stubborn fights I have seen the men on both sides sit on their restless horses and re-load their pistols under a galling fire. This was not a custom, however; someone generally ran to cover after the revolvers were emptied.  We both did this a good many times but, I believe, without bragging at the expense of truth, that we saw the back seams of the enemy's jackets oftener than they saw ours. . . Revolvers in the hands of Mosby's men were as effective in surprise engagements as a whole line of light ordnance in the hands of the enemy. This was largely because Mosby admonished his men never to fire a shot until the eyes of the other fellow were visible. It was no uncommon thing for one of our men to gallop by a tree at full tilt, and put three bullets in its trunk in succession. This sort of shooting left the enemy with a good many empty saddles after an engagement.
For instance, describing the fight at Miskel's barn, Munson says of William H. Chapman (later lieutenant colonel of Mosby's command) wheeling his horse in a thicket of Yankees "[t]he pistols were not a foot apart. The Yankee's pistol snapped [misfired] but Chapman's did its deadly work. He fired six shots and emptied five saddles."
A few guerrillas equipped themselves with carbines captured from the Union, but "they were unhandy things to carry" and unsuited for fighting on horseback; indeed in the thick of a February 1865 fight the carbines' long barrels made them too unwieldy to fire, and they were used instead as clubs. Mosby tried out some small field artillery pieces, including a 12-pound (5.4 kg) brass Napoleon, but artillery proved to be too cumbersome for his fast hit-and-run tactics and not especially helpful in action. Ultimately Union troops found the mountainside hiding
43rd Battalion, Virginia Cavalry