Whether you need a lighted hard drive or not certainly is a personal decision. If you use your drive for backup purposes only, there might not be a lot of sense in getting this tricked-out $300 version. Yet it might look great on your desk - assuming that your host system isn't located in a very bright spot, which will kill the drive's light show.
The two fluorescent tubes will stay at a certain color until you press the control button. The lighting will then start to cycle through all the colors it can generate, which is basically the whole spectrum. Luckily, the cycle speed is not too fast, so nobody should be in danger of suffering an epileptic seizure :)