A bandanna is possible the most useful bit of kit anyone can carry.

They are water filters, bandages, field expedient socks (portyanki), and loincloth (emergency replacement underwear or swimsuit). A string around the waist, possibly a narrow strip ripped from the bandanna and twisted to form a cord, and a narrow rectangular cloth formed from the larger piece by folding or cutting.

My favorite are simple unbleached cotton muslin sold as a 'triangular bandage', that are typically about 30" square, and sell for a bit more than $1 each and often come with a couple of cheap but handy safety pins. You can dye them any color you like but the natural off-white looks good to me. I'm not willing to pay an extra $5 to get the OD green version.

Thanks Marks, that's a good idea. I'm off to raid my wife's supply of fabrics!:-)

Any size is OK, but I fint that the bigger ones are more useful. You can make them from cotton cloth, they don't have to be fancy.

OK, I'll take the bait. Red is certainly better for bullfighting, but for all other applications, I recommend olive green. Looks great tied on my head with a long tail, and it attracts rich and beautiful women.

Howdy Everyone! If you are fortunate enough to have a 99cents only store in your locale,they regularly stock 100% cotton,22"x22" Bandanas in just about every Hue, you could desire.They all have that fancy:Cowboy Paisley pattern,printed on them,however... they are Definitely made Elsewhere,so I've handwashed mine,a few times,with Castille soap/Cold water.

Another use, You can blindfold your self. If you do not actually have to see the perils you are facing you can be less scared!

Sorry I had to.

More uses: Trail marker, and a pretty flexible dump pouch (tinder/edibles/morels)

If you get a white bandana, you can use it as a French Battle Flag....

Yeah, respectfully, I'm a little cautious about revisionist history, as the final accounting tends to point in an inconvenient direction. But hey, that's me, YMMV.

Returning to the OP:
I think the best bandana is a chunk of synthetic chamois. It weighs nothing, and it absorbs many times its weight in liquid. So, it washes and dries skin and hair, it absorbs blood if needed, and it is largely indestructible. If only it came in red, it would be perfect.

use 42: Pad. protection from snow/ice/gravel/sharps.
Today I locked my keys in my truck with a couple inches of snow on the ground. (Late to class and rushing) To get to my hide-a-key underneath my truck I had the pleasure of kneeling in the snow. I don't really enjoy a soaked freezing cold knee, so I ran through my options. Rather than trying to get in the snowy bed of my truck to force open the sliding glass window and slip and slide on my plastic bedliner, or using books/papers in my bag as a barrier (terrible waste of paper and would upset my instuctors "I had to kneel on my homework sir, I will have to re-do it.") I decided to use my bandana folded several times over. Kept my knee dry, and dried out on the trip home. I have put it back in its designated pocket, so I will know where it is.

My first truck came from a repo auction and had a small hole in the floor (a plug should have been there). I duct taped over the hole and tapes spare keys to it. One winter I started the engine and got out to scrape the window and out of habbit locked the doors. I thought no pboblem I get my spare taped over the hole like I planned. Punched my hand through the hole and heard the keys ping as the bounced around in the bac. had to reach my arm in and finally was able to reach one, unlocked my door and drove home. When I got home I relaized the key i had reached was the square head which fits the igniton so I went out and tried it in the door and it wouldn't work, yet somehow earlier it did. Someone was watching over me that night.