Green roots, chartreuse roots, yellow green roots, it really doesn't matter what color they are. When Vanda roots go from white or gray to green/ yellow, they have absorbed water.
I think that your Vanda may be suffering from a lack of fertilizer and Vandas are one of the few types of orchids that are heavy feeders.
How long have you had the plant?
How often do you fertilize?
With what?
You can actually hang a small little nylon bag of fertilizer at the base of the Vanda stem. Some slow release 20-20-20 would be nice, a tablespoon would work. Every time you water, food will be realeased. I don't think you have bugs or a root disease. I think you have a fertilizer problem.
Being in Jacksonville, keep it in warm air year round. They don't like temperatures below 60*, 50 on rare occasions!!
When is the last time it flowered?? Vandas love heat, water and fertilizer. You can't over water or feed them too much. I think with good sunlight, 5-6 hours of sun and really bright light will pump this bad boy right back up! That and some fertilizer!
