A recently study at the University of Phoenix suggests that water with a slight blue tint is the most relaxing for eighty percent of study participants.
In the study, volunteers were connected to wireless devices measuring their heart rate, skin conductivity, and overall muscle tension, and then shown to a bathroom. The water in the bowl had been dyed with differing colours including red, green, brown, blue and plain. The blue tinged water consistently caused the least tension in participants, with red causing the most.
When asked questions about their experience, the small number of people who found the blue water less than relaxing were more curious about why the toilet would look like it had just been cleaned when they had seen fifteen other people enter the same washroom before them.