Answer

You can use the LED_SW on the motherboard to turn off the RGB light.

Models

MPG Z490 GAMING EDGE WIFI, MPG Z490 GAMING PLUS, MEG Z490 GODLIKE, MAG Z490 TOMAHAWK, Z490-A PRO, MPG Z490 GAMING CARBON WIFI, MEG Z490 ACE, MPG Z490M GAMING EDGE WIFI