The visualization of changes in the stress and bonding state inside polymeric materials is an attractive function in materials science. In this study, phenolphthalein (PP) was selected to prepare stimuli-responsive coloring materials. PP becomes purple under basic conditions in aqueous solutions; however, PP becomes colorless under basic conditions when it forms a complex with beta-cydodextrin (beta CD). To exploit this property of PP, we prepared a color changing hydrogel (beta CD-PP AAm hydrogel) based on acrylamide (AAm) as the main chain and beta CD and PP moieties as the side chains. The beta CD-PP AAm hydrogel exhibits a color change when heat or a competing molecule is applied at a pH less than 8. This color change was confirmed by ultraviolet visible (UV-vis) spectroscopy, and the mechanical properties were determined via compression and tensile measurements. The beta CD-PP AAm hydrogel also exhibits a rapid, reversible color change upon Joule heating produced by an electric current passing through the gel.