Sorry I should have made myself more clear. It's ok to blend protein and water/milk overnight. But if you are blending with fruits etc, it would go brown overnight.
I agree with the above. It is fine to store the water or milk and just protein over night. But if you add fruits then I'd say don't do it. Gonna taste like bad.
Use a protein cup shaker so then in the morning you can just toss in 2 scoops of protein and cold milk or water and shake it up.
But I have used in the blender in the morning when I was going to the gym at 5am or when I'd get home at 7ish am. BOTH GOT ME YELLED AT!!! haha