Edible electronics present new opportunities for food-integrated sensing and monitoring, yet powering such devices safely and effectively remains a major challenge. Here, we introduce a fully edible thermoelectric-electrochromic platform capable of converting heat from food into a visually perceptible color change, such that this platform can be used for real-time temperature monitoring. TEGs are fabricated from vanillin-crosslinked chitosan and alginate hydrogels functionalized with potassium chloride used as an electrolyte. Positively charged chitosan acts as a p-type hydrogel, whereas the negatively charged alginate serves as an n-type hydrogel. To increase the voltage of the edible device, we connect multiple p-and n-type hydrogels in series. The resulting TEGs successfully drive anthocyanin-functionalized, gelatin-based electrochromic displays that are purple at room temperature and blue when the temperature exceeds 45°C. Transient heat sources, such as a freshly heated cake, are sufficient to trigger the color change. This work demonstrates that fully edible materials can be engineered to harvest thermal energy and convert it into a visible signal. The platform establishes a foundation for safe, biodegradable, and ingestible devices for on-food monitoring, transient electronics, and food safety applications, offering a new approach to integrate sensing and display functionalities in edible systems.