When water flows down,the LED will light instantly and automatically; Brightness is such enough even no other lighting fixtures need. When water temperature is ≤32o C,Green color will show automatically; When water temperature is between 33o C 41o C,Blue color will show automatically; When water temperature is between 42o C 45o C,Red color will show automatically; When water temperature isabove 46o C,Red color willflash immediately; This item will change its color by detecting water temperature.