I have the DKS2 reds with green LED's.
I can confirm that on maximum brightness, set to always-on, there IS an electrical type of hum which can get annoying if I'm not wearing my headphones. Those freaking LED's can go so dang bright though, so I'm not surprised to actually hear that electrical hum / buz.
Edit;
I bet on pc's with more powerful PSU's you don't get the buzzing. I'm running a Dell XPS laptop - not exactly a power-house of a computer.