The big coloured circles are to allow people upload avatars.
I find avatars very irritating and just adding to the clutter.
They might have some value if people uploaded their actual photos - which I have done to illustrate.
If you click the New Posts Button - you will see only the New Posts which you have not read.
However, just above the first post you will see "Show only unread" . Click on this to remove the unread filter which will allow you see all posts.