genuine question, because I forgot a $20 with the laundry at work and I don’t know if the laundry is going to look green or if I’m going to get a white $20 back and clean clothes…
Bills are made to be able to go through the wash for the exact reason that yours ended up in the wash, people carry them around in their pockets and it’s easy to miss or forget about. The bill might look slightly more worn but it won’t have all the color washed out or anything like that, assuming you didn’t dump it in a load of whites with a ton of bleach. It shouldn’t hurt your clothes either.
I think the washing resistance is more so to prevent counterfeiting in which people bleach bills and print them to be higher denominations.
It functions that way as well, but durability for every day use is also a consideration in the material choice. Bills being uncounterfeitable isn’t particularly useful if they’re constantly being removed from circulation because someone left a bill in their jeans when they washed them.