I just moved into my house with brand new PEX (uponor) plumbing. I used clear for the hot and cold instead of red and blue, because I bought everything myself and I thought it would prevent wasting too much. I installed the PEX tubing myself after buying a new Milwaukee tool. This was my first PEX DIY project, but I have a fair bit of experience with lots of remodeling trades.
Anyway, we have been using the plumbing for about 6 weeks. I just noticed that the hot water tubing right near the water heater (commonly abbreviated as HWH) now has a green hue for about 12-24" past the heater. The water itself is not stinky or green - although I do notice a slightly different smell than with my old copper plumbing. There is about 3 feet of SS flex and copper between the water heater and the PEX. Our County inspector approved everything. The water heater is electric and it is about 5 years old, purchased from someone on craigslist. The water heater was empty when I moved it into the house, but I didn't try to clean it with anything.
So, what is causing the PEX tubing to turn green? Should I make the water heater hotter? I don't think it is above 120F, but I haven't measured it. Should I figure out how to inject bleach into the system every once in a while?
Edit: added picture. It turned out better than I expected.