OT: How to disable the lights on modern case fans

I just replaced a crashed machine with a new one (as always DIY built)
and the new one is a good replacement for a VM only host except for
one thing it has all these spinning/blinking colored lights on the
case fans (and the CPU fan).   I have searched the BIOS settings to
hell and back and can't find any setting even related to this.   How
do I turn the damned things off (it is making it impossible to sleep).

-- 
Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org