Thought one of the colors "blocked all spells"? Which would not be a problem for a wall since you could.. umm teleport around the long way...? But I could see not being able to teleport into a sphere.
I take "stops all spells" to mean that you can't cast any spells through the wall/sphere (i.e. it blocks line of effect). When you're inside the sphere, you can still cast spells on yourself, such as Cure Light Wounds or Teleport or Plane Shift.
