In the old system, the ones you had looked at were blue, the ones you hadn't were yellow-ish. A thread that you had posted to had a black dot on it.

In the new system, a thread I have posted to has an arrow, a post I have read is blue, a post I have not read is yellow-ish....except that it doesn't appear consistent. Some threads have the yellowish icon, but I am the last one to post something to it. Therefore, it seems that it should be blue. What do the colors mean? How do you tell when somebody has posted a reply? Is looking at the last poster name the only option?