In this work, a color-oscillating system is first developed by combining the intrinsic peristaltic motion of a Landolt pH-oscillator with the structure color of a well-designed pH-sensitive photonic crystal hydrogel. As a result, the pH oscillation reaction procedure could be distinctly monitored by the distinct change of structure color/optic signal. The oscillation rhythm of the pH well coincides with that of the stopband/structure color. The oscillation detail of each cycle can also be clearly monitored by color change. This work would be of great significance for the promising applications of real-time monitoring of the microactuator by optical signal or structure color.