Orchid with white roots?

[Bulbopedilum]

I have experienced what you are talking about. I half-killed my oncidium with hard beatings of sun rays and water-in-tight-spaces (rot). All the roots where dead white, but then I repotted it into chopped up tree fern fiber (it used to be in weird fern fiber blocks) and now, 4 months later, it's doing great, growing a new pseudobulb and new roots, even grew one weird root that creeped up on one of the pseudobulbs lol! It's not a miltoniopsis but maybe you could take some tips.