A lot of the bandanas on the market now are not 100% cotton. And bleeding is another problem with some of the current bandanas.
As an aside, when learning to iron, my first pieces to tackle were Dad's bandana handkerchiefs - red ones and blue ones. Eventually I was trusted with his blue chambray long sleeved work shirts. I still have a fondness for those items and wish I had the privilege of ironing those for him now.