Steps to reproduce:

1. Open attached project "SphereColliderBug-12June2015.zip"
2. Open "SphereColliderBugScene" scene
3. Press play and make sure that "Gizmos" are enabled
4. Press and hold right arrow key on keyboard to move "SimplePlayerObject"
5. Move over both of the spheres and notice inconsistency in surface normal directions (attached inconsistency.gif).

Note: normal of collision with SphereCollider seems to be inversed compared to collision with CapsuleCollider. I have also attached 4.6 project where this inversion isn't present (SphereColliderTest4.zip).