Sharon, I had the same issue... but I found that if I go to the individual forums (i.e. Conures or Off Topic), then click on Forum Tools (right below page counts) and Mark This Forum Read, then all posts will be marked as read in that forum. Can be annoying if you don't read many posts, but it works.
After you have read a post, and go back into New Posts, the most recent ones you have read will appear in a lighter shade of blue. When logging in again, they will all appear in a dark blue shade.