Fn+F5 key will only enable/disable LED for keyboard area. The speaker lights (left + right) aren't control by this key combination. A trick to turn off the speaker lights is to use HP OMEN Control and set speakers light color as "black".
Note: By default, all top-row(F1-F12) function keys (volume up/down, brightness..etc) requires holding Fn key + Fx key. You can actually skip the Fn key by changing this default behavior from HP OMEN Control - Advance tab. Cheers!
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