I've noticed that orchid roots often grow away from the light. It makes sense to me because roots growing away from the light will have a better chance of finding the tree branch that the orchid is attached to. Cattleyas seem to have even more of a tendency to do that than phals.. Some phals seem to like to grow lots of aerial roots and others are more apt to grow roots into the media. You just never know what they're going to do. It's in the DNA I think.