The Wheel of Time - The Call of the Horn
Color-shifting cloaks are special garments that are unique to Warders. Made out of a special material called fancloth, they seem to mimic the surrounding landscape and serve as camouflage.
Warder’s cloaks tend to invoke a disturbing feeling on people who see them while they are moving, and while stationary the wearer blends in nearly perfectly with the background. The cloaks are somewhat of a trademark for Warders, and as such, can be used to recognize a Warder and his Aes Sedai on sight.
The fabric for the color shifting cloaks is made by a certain ter’angreal in the White Tower which has no other known use.