Longstreet's Corps made an impression on the Western soldiers they encountered and more than one recounted the appearance of Longstreet's men, over the years several stories have been told about where they aquired their new suits, for those who are unfamiliar with this, Longstreet's troops wore light blue pants and dark blue-gray jackets. The following sheds a little light on this and also shows that it wasnt exclusive to Longstreet's men, but the Army of Northern Virginia as a whole;
"I heard it from a courteous member of General Lee's staff, who has recently inspected the army, this its fighting condition never was better, and that its comfort is duly cared for a its health all that could be desired. I, myself, can bear witness to the truthfulness of all that can be said of the morale and spirit of this army just now. It is, I humbly submit, the most agreeable news that I can communicate to the home folks, that the Army of Northern Virginia is being supplied cap a pie with new outfits; and I hazard nothing in saying that in looks and spirit, out troops are today in nothing behind the condition of the army when it entered Pennsylvania; and yet, so silently has this metamorphising process been conducted, and so quietly is each department discharging its duty, that you can scarcely realize how so great a change has been wrought in so short a period."
That account is from the August 30, 1863 issue of The Charleston Mercury. It should also be noted that Longstreet's men boarded the trains south on September 7th, 1863.