Yes — blueberries are packed with antioxidants and perfectly sized for small beaks.
What it means for African greys
There's nothing specific to a african grey that changes the verdict on blueberries — it's treated the same as for parrots generally. Greys can take a larger portion than small parrots.
The full picture on blueberries
Blueberries deliver anthocyanins and vitamin C in a bird-bite package, with less sugar than most fruit. No seeds to remove, no skin to peel — one of the lowest-effort, highest-value fruits in the bowl.
Rinse well and serve whole; halve for budgies.
Frozen-and-thawed work fine and are cheaper off-season.