|My Clarisonic is a boring white, which really shows every bit of dirt on it.|
I have had mine for a little over a year now (read my review here) and I still love it. I've changed my brush heads twice and I pretty much use it everyday. As you can see, my unit is white and since it gets wet, it has started to look grayish and a bit moldy. Gross, I know, but there was nothing I could do about it. I tried scrubbing it with shower gel, even tried diluted bleach but the grayish grime was still there. I didn't dare try harsher cleaning agents because I didn't want to risk damaging it.
You know what surprisingly worked? Plain white toothpaste.
I discovered this by accident; I dropped a gob of whitening toothpaste (mine was Arm & Hammer, but I suppose any brand would do) on the back of my Clarisonic one morning and didn't notice it until I needed to use it that evening. I just wiped off the toothpaste when to my surprise, the spot where it sat on was back to its original pristine color! I excitedly slathered toothpaste all over (without wetting it at all) and when I wiped off the toothpaste, the stains were gone. So now I can bring it again on overnight trips without being ashamed of other people seeing it.
So that's it. If you do try it out, do let me know how it works for you!