What is causing it to fluoresce is they appear to be using LEDs in the 420nm (true violet) range with a fluorescent dye in the liquid coolant.
Short-wavelength LEDs from 450-390nm are often used to "excite" symbiotic algae within corals for people who own reef aquariums. But too much light can actually wash out the effect and make it hard to see (too much white light).
So in order to achieve this look you 1) need a liquid coolant with some sort of fluorescent dye in it, 2) need some 420nm LEDs (they're responsible for a large portion of excitation and are more difficult to be picked up by the human eye), and finally 3) you need to not have much other light to wash out the effect,