I've been taking a lose dose of Adderall for about 4 months and I'm noticing a discoloration in the backs of my fingernails. Its a bluish color and sometimes creeps down the nail further. I switched to Dexedrine and its still happening. I notice it more when the medicine peaks and during a comedown, both periods when my adrenaline is low. Taking a body stimulant like caffeine seems to reduce the effect.