Cotman watercolor test strip
The strip for the test was subjected to extreme sunlight with the exception of a few cloudy days. This is Southern California and the sun in the summer is intense. I tested the paints for close to two months. I felt that was enough (I'm not obsessive about this). This isn't the greatest scan, unfortunately, but happily there is no noticeable shift in the color. Please note that the Cadmium Yellow Hue is lighter where the strips meet but that's because, by accident, I lifted the paint when it was wet.
You'll note that a lot of these paints are hues. They work fine.
I used 8mm tubes, but in the future, where possible, I'll be buying 21mm tubes.