Are there any motherboards that don't allow you to turn off the RGB in BIOS? Even my crappy Biostar board has that functionality. Find a board you like and look up a review of it. Any decent motherboard review contains a thorough BIOS walkthrough. Or do you mean disabling ALL LEDs, including status LEDs? That will be more of a challenge.
Also, creating a thread and then waiting a whole six hours before following up with a snarky response complaining about no replies? Yeah, that's not how you make people want to help you.