They have the same temperaments as any other GSD !
From my favorite source Wikipedia: The White Shepherd has a distinct personality marked by self-confidence. The breed is poised, but when the situation demands, it is eager, alert and ready to serve in any capacity. White Shepherds demonstrate both herding and protective instincts. With those he knows, the White Shepherd is open and friendly. With strangers, he is observant and may be somewhat aloof but not apprehensive.
...This is a joyful, active, intelligent and easy to train working dog with the ability to adapt and integrate to all kinds of social events and situations.Timidity in a mature dog or aggressive behavior is not typical of this breed.