New Legion series have integrated changing LED in the power button to indicate different power modes such as quiet, balanced and performance. In this case red light stands for performance mode. You can press the fn + q and see the modes as well as lightning change from quiet (blue) to balanced (white) to red (perfomance).

https://www.reddit.com/r/Lenovo/comments/kp05cd/red_power_button_does_anybody_know_why/