To achieve a layered look, blend the peach, blueberry, and vanilla layers separately. Otherwise, blend all ingredients together.
Vanilla Layer: Add 1/4 cup frozen Greek yogurt, 1/4 cup almond milk, 1 tbsp casein protein powder, and 3-5 large ice cubes to blender. Blend until smooth, set aside in freezer.
Peach Layer: Add 1/4 cup frozen Greek yogurt, 1/4 cup almond milk, 1 tbsp casein protein powder, and 1 cup frozen peach slices to blender. Blend until smooth, set aside in freezer.
Blueberry Layer: Add 1/4 cup frozen Greek yogurt, 1/4 cup almond milk, 1 tbsp casein protein powder, and 1/2 cup frozen blueberries to blender. Blend until smooth, set aside.
Add the vanilla, peach, and blueberry layers in a large glass. Top with whipped cream if desired before serving.