What have you added to the water? Any nutes? Could be tint from the additions. Are the roots slimy and do they smell? Get yourself some hydroguard and you need to worry about root rot.
I'm using 1/2 strength of what they recommend, with Advance Nutrients. The roots aren't smelly and there's no slime. I've been using Hydroguard. 2ml per gallon, once a week.