Ok first the roots.....Smell them if it does not stink then it's not rot. From what you are saying then you are correct about it being colored by the nutrients. You can add some H²O² (proxide) to your water 5-10 ml per gallon with each water change. That will bring back the white for you.

As for the cool tube.....You will need a MOG socket (they don't sell them at HD) but most hydro stores or electrical wholesalers do. ) They make cash sales over the counter. Good place to get bulbs too btw.
From HD you get:
2 4" vent metal collars
2 4" hose clamps
1 Roll of window foam weather seal tape (thin)
1 4? angle bracket
1 roll of metal silver foil tape
Either pop rivets or small nuts & bolts to assemble.
(x)ft of 12 gage 3 wire extension cord
That will make one unit.