The name in blue is a hyperlink to a page that gives some info about you. Some of us list our email addresses, others keep their email address "hidden" because of sin and depravity!!
Those who haven't joined are not in blue.
Two nice advantages to joining:
1) You can correct a submission (for about 24 hours)
2) When you open a thread, new submissions since you last viewed that thread have the word 'new' in read next to the title.