[NathanthePie]

It's possible that when nobody is working in the room, the lights aid in maintaining a sterile environment.

At specific wavelengths (~245-265 nm), (UV) light inactivates quite a few living things. As light is quantized, the purpleish color you see is due to e- stepping down.

[escherplex]

My UVC bulbs deployed in a FL home water treatment system pipe out UV in the region of 253.7nm. An ophthalmologist friend pointed out that unfiltered long term exposure to these wavelengths first catalyzes conjunctivitis (pink eye) then conditions go down hill from there. It's suggested that you don't stare directly at sources of this purplish color for any protracted periods.

[kale]

Nope. Our bio hoods have a toggle switch. Lights off is in the middle, lights on is one direction, UV sterilization is the other direction. To turn the lights on, you have to turn the UV off.