Brightly coloured ones need to be made from very stout material owing to the chemical effect of the dyes upon the cloth, you know.
Curiously this effect is confined to the threads that are in horizontal tension (the Warp) and not to those which are in vertical suspension (the Weft).
Catastrophic failure of chemically imbalanced materials is liable to result in your thin-thong being turned into a play-a-round and everybody being chucked out of the pub.