"This fancy hotel has a shallow tub with two sides. When the button is pressed, one side lights up with a red light and hot water for about 30 seconds. Then the other side lights up with blue light and cold water and shuts off after the same amount of time."
A: "This is very common in Germany, we call it “Wechselbad”. You’re supposed to keep your feet in the warm water first and then quickly put them in the cold water (repeat a few times). This is supposed to help with circulation although I’m not sure if there’s actually scientific evidence for that."