I just noticed this, and it bothers me. Happens for other color combinations as well. this is madness
That's because you've read all the threads in that subforum - just like a link to a thread becomes non-bold once you've opened the last page of that thread, these text bubbles slightly change colours to show that all threads have been read.
It works that way for me though - I do have to note, in the Empire Updates section, I believe it has randomly set all threads as read, because I don't think that I read all of the ancient threads in there.
It indeed looks like that's the thing that happens... (luckly enough it's spoiler free, so I may post it) As you can see, this one is lighter inded, and, that indeed could be becuase I have read all threads in that subpage. What I think you might have done is click this button here: (top right) I think that when you click that button, it will make it lighter yellow, I don't want to test it though.
