I can't officially say from the photo, but that looks like the velamen (the spongy outer covering layer of the root that will turn silver-white in color when dry) is just turning and the plant is indicating that it is in need of a watering. In well-established phals, you can also sometimes see a little bit of "white hairs" growing off a root and attaching themselves to either bark or the pot it's growing in- these are anchoring hairs that help hold the plant within its media (they grow in trees in nature, so they need to have that ability to hold on and not fall out of the tree). I think that your phal is okay- just thirsty