No need power supply or batteries, turn on the water and the light will turn on!
It's perfect for baby bath.
Color changes depending on the water temperature. When the water temperature is ?32 °C, the lamp will glow green. When the water temperature is between 33 °C and 41 °C, the LED light will emit blue light. When the water temperature is between 42 °C and 45 °C, the LED light will emit red light. And when the water temperature is ?45°C, the LED light will flash red.