The Latin Rule also referred to as the "Specific Behavior for the Templar Order," is a document that organizes all aspects of the order's members' lives. It also details out what is allowed and is not allowed in garments.
While knights wore white mantles, sergeants wore black ones. In the 12th century, a red cross was added to the garments. There was a draper that distributed the garments to the Templars.
The Latin Rule provides more information about the dress code of the Knights Templar. The first principle is that all "the brothers" should be dressed in a single color, as a uniform and religious clothing. The color is preferably white, as it stands for purity, not just of heart, but of the body too, as everyone who wore white took a chastity vow. Every member who joined the Templars is considered to have abandoned the life of darkness and is finally united with his creator. Even though married men were allowed to join the order, they were not allowed to wear white as they didn't take the vow. The Templars mantles, however, shouldn't show a sign of pride or wealth. Blankets, on the other side, were only allowed if they were made of a lamb or a sheep's wool. Everyone in the order needed to dress the same way, and the order's draper was responsible for distributing garments that fitted perfectly. Not only that, but if a member showed pride in his appearance, he was punished.
Also, all members needed to send their old mantle back, to be given to the poor, once they receive the new one. However, a linen shirt was allowed considering the heat in summer times. The rules included bed linen too. Members could only have one blanket, one mattress, and one bolster: a narrow pillow. In their sleep, the "brothers" of the order needed to be in their shoes, shirts, breeches, and belts.
In fact, the Latin Rule also had regulations concerning shoes. All shoelaces and appointed shoes were utterly prohibited, as those two items were usually worn by pagans.