Elevated temperatures at the transformer bushing cylinder head can precipitate failures, leading to significant power outages. In response, this study introduces a reversible temperature-indicating patch for the nuanced detection of thermal anomalies in the transformer bushing’s cylinder head. The patch, crafted through a melting process, utilizes a reversible discoloration material and is developed in two variants via an adsorption substrate method. Comprehensive evaluations of the patches’ color-changing characteristics, alongside their electrical and hydrophobic properties, were conducted using an automatic contact angle measuring instrument and an AC flashover test platform. The findings reveal that the temperature-indicating patch exhibits a discernible color transition within the range of 49~55 °C, with a color reversion temperature span of 45~55 °C, denoting marked sensitivity and robust reversibility. Additionally, it was observed that prolonged thermal aging correlates with a decrease in both the water contact angle and the discharge voltage per unit length across the surface of the patches, indicating a degradation in performance. Among the variants, the binder-based temperature-indicating patch demonstrated superior stability in electrical performance compared to its vacuum-based counterpart. The outcomes of this research offer valuable insights for the development of advanced diagnostic tools for the identification of thermal defects in transformer bushings, potentially enhancing reliability and safety in power distribution systems.