Testing acids and alkalis using universal indicator
Acids turn red when an indicator is added.
You would try to kill a zombie with a bath of acid, which would turn red if you did! (Acidic solutions turn universal indicator red).
A neutral solution (like water) will turn green.
Think of a gear stick sticking out of a chameleon; when the gear stick is in the neutral position, the chameleon turns green.
An alkaline solution will turn universal indicator blue or purple
Bleach (an alkaline) comes in a blue bottle.