Paring with wrong keyboard in morning

MY PROBLEM: Is there any way to remove the Apple wireless Silver keyboard from my computer so it doesn't pair anymore? I can't seem to find anything in the Preferences on that.

BACKGROUND: I have an iMac with the standard white wireless keyboard and decided to try out the Apple silver wireless keyboard my business partner had for his MacBookPro. Didn't like it and gave it back.

He's now using the silver keyboard with his MacBookPro, but every time he comes in in the morning (I'm usually the first one here), his keyboard continues to pair with my computer though I never see the "Keyboard connected" icon come up.

Thanks in advance.... Red

System Preferences > Bluetooth > and delete the aluminum keyboard from your paired devices.