I recently saw a video on YouTube in which water, when mixed with a solution (I believe iodine was involved,) changed color based on its acidity. I am attempting to replicate this experiment, but cannot concoct the solution. Any help would be much appreciated.
EDIT: To clarify, if I had water with a ph of 10 it would turn red, but if the water had a ph of 4 it would turn green.
EDIT 2: I found the video in question http://youtu.be/_yi83kOB8ug