Cargo for coat

Will food colouring mixed with water stain my bath tub? what can be used to remove the stains? - what can i put in my bath water

I am a bloodbath for one of my scenes in the movie, but I'm struggling with what the substance is used as follows for blood. I have the color in water at the previous scene, and does not stain on the cup, knife, or a counter. but it stains the tub? I put a lot of water?

I will not give up the bathtub full premium rate for a player to sit down. I want only small drops in the tub.