Welcome Peter, This forum is a powerhouse of information on all your drug related questions, or so I've found it to be so far .
I'm pretty fresh here myself but it's still great to see new members signing up.
Tell us a bit about yourself, what’s your drug of choice etc.
If you have any questions I've found all of the Mod's / Admins to be most helpful so feel free to ask away. I also recommend heading over to the basic drug discussion forums for a good place to start.
As for the difference in a Greenlighter and a Bluelighter: your status will change to Bluelighter after you have racked up 50 posts. This will give you access to posting in the lounge as well as a few other benefits. I recommend reading the Greenlighters guide available in the green box towards the top of your page.