Why do the links in a plastic chain become different colors?

I have a plastic chain, about 5 meters long, sitting between two wooden posts. The link has 1 meter long sections of alternating white/red links. It's been sitting there for 2 years, and the once red links have now become purple/pink. I always just thought it's because of exposure to the sun and "the elements" and didn't think much about it.


But today I noticed something strange - the links between each section of white and red are a very different shade of red than the red links inside the red sections.


How can this be? Is there some chemistry going on between the links which makes the color less faded in the ones that are touching one red and one white link?


I am not 100% sure, but I definitely don't remember any color difference when the chain was new - all the white links were the same white color, and all the red links were the same red color.


[![enter image description here](https://i.stack.imgur.com/3Edxv.jpg)](https://i.stack.imgur.com/3Edxv.jpg)


