I'm fascinated by iridescence - I wrote about it here and here. A recent study of the iridescence of insect wings when viewed against dark backgrounds was conducted and the resulting pictures are fantastic. Check it out here or here.
Here is a photo I took yesterday of my jar experiment (I started it here). I'm now eleven days in and the water inside the jar still looks slightly yellow. I don't think there has been any change so far. Perhaps the jar should be moved into direct sunlight (which isn't possible in my office).