Galilean thermometer photobleaching

My brother bought me this Galileo thermometer (Wikipedia) as a Xmas gift in 2008. Out of the box, it looked very like the manufacturer photo shown at extreme left. The near-left picture was taken just today.

Over the intervening three years, it has been displayed continuously in one window or another, windowsills being not only useful locations to observe the temperature, but good places to show off the strikingly beautiful colors of the instrument. It was only a month ago that I noticed the blues and greens had faded away. I have noticed a similar effect in a pair of full bottles of Bomba energy drink that have also been kept in the sun (and for about the same length of time): the red is still red, while the blue has faded away. (Update: My memory of these bottles’ original colors was flawed. See this post.)

It’s likely the soda, at least, is dyed with Brilliant Blue FCF, aka Blue 1 (Wikipedia), and I wonder whether the Chinese-made Galileo thermometer also might have used the food-grade dye. It would be a sensible choice, for a manufacturer; with US consumption estimated at a million pounds a year, Blue 1 is dirt cheap, and obviously nontoxic, which the underwriters probably favor against the chance of an accident in which the thermometer breaks and the stuff gets into a human orifice or wound.