 Either the color is the consequence of urine or is the color of the chemical put into disguise the urine or is the reaction of urine to chlorine or some other unknown chemical agent. I don't doubt urine is involved. I have peed in there myself. But it's not the urine that we find so disturbing. No, the sad consequence of the green is that it concentrates the mind in a very unpleasant way upon the artificiality of the lazy river.