as u said you are on propranolol
, & you are experiencingfingers & toes turning white when you exposed to cold
, this suspects me of raynaud's disease. as propranolol precipitates the raynauds phenomenon if suscepteble.
avoid cold temprature & emotional stress
please do contact your doctor by telling above symptoms
Hope it helps, Take care & plz do keep me posted on how you doing or if you have any additional doubts