Oh, and regarding the light, I don't think you can use green light with the roots since they are white/brown. The reason green works with the plant is, I believe, because the plant is green itself.
Also, if you are going in and out alot, even with a green light, you're allowing potential other light to come in as well, and, your green light may not be the exact right wavelength. Doing this often is asking for trouble, I think most growers view the green light as a kind of last resort when you absolutely have to get in the grow.