The Red Rag, otherwise also known as the Dead Rag, is now gathering steam for more widespread adoption outside of the USA where it is already a common thing as a hit marker rather than always shouting that you're hit on your way to the regen zone, or for a medic to easily spot you. It is such a lowcost piece of cloth that  you can put on your rifle or your head rather than strain your arm as it's constantly raised.