1 As the built-in device generating electricity without the battery and any other power connets to water, LED will emit the light. 2 When water flows down, the LED will light instantly an automatically; A When water temperature is d32 , Green color will show automatically ; B When water temperature is between 33 -41 , Blue color will show automatically; C When water temperature is between 42 -45 , Red color will show automatically; D When water temperature is above 46 , Red color will flash immediately. 3. This item will change its color by detecting water temperature.