Just a WAG but something in your cache is remembering the previous state of the system on your browser. If it's changing and then you go back, it's new again?

Try clearing Internet Cache.

Otherwise, there's no reason for them to change to the selected "previously viewed" status, and then revert to unread colors.

You might also try changing the color to something like GREEN save, and then change it back, SAVE. A little kink in the settings, might give it a wake up call.