have to be painted white
 

why do the bottles you grow in have to be painted white, will the light from a HID lamp hurt the roots if the bottle is not painted please take the time to fill me in on this You are the only person I trust getting information from that wont put my garden at risk please respond and keep up the excellent work. CLUELESS

The bottles are painted to help cut down on the algae buildup caused by the light hitting the water in your garden.
A lot of people are concerned about the algae in hydroponic gardens. Even though it's not pretty, algae is your friend. You can't grow with hydroponics and not experience the green slime.
Algae is a sign of healthy water and robust life; not a sign of contamination or problems and only becomes a problem when it grows so thick as to cut off oxygen to the plant beneath. If that happens just rinse with tap water to remove.