I am sure it has been mentioned before but what I do is this:
I use a label printer to make stick on label of all my powders-usually 2 or 3 for each powder and stick 'em on the jug.
When I fill the hopper I stick on one of the labels on the hopper and leave it there til I pour the unused powder back--overkill, probably but I ALWAYS have a label as to the powder.
If I would get pulled away unexpectedly there is never a doubt what is in the hopper.
Guess that is what being OCD does to you

)