Yellow pencils and red pencils have to do with your "PMs" (personal messages) in your "inbox". If it's "yellow" you've read it, if a red pencil appears it means you haven't read the last PM.
Yellow Stars -- you can 'rate' a post as to how helpful you feel it is. The stars at the top of the thread -- you can choose stars to indicate to someone else you found it very helpful.
The green lines under your avatars - if you hold your cursor on the line it will tell you what degree of contribution someone is. Like Bevolasvegas/Amanda is a "top 25 contributor". Mine says something like "Mega Blabbermouth" or something (*rolling eyes*)
POints are this completely mysterious entity that none of us have quite fathomed yet. To be perfectly honest they are completely useless. The best any of us have been able to ascertain is that you get points for "stuff" (scientific term that .... *grin*)
You get points for posting, for uploading photos, for answering a post that no one has bothered to answer, for blogging, and even for reporting spam **I think**.
My gut guess is that was something the makers of the messageboard "software" intended could be used as a reward system -- of course we've always hoped that Dog.com would say "use your points for money off" ... but, hey, they give us free webspace for all this posting and don't charge us for it -- I figure we "win" right there!!! Essentially points are these invisible things we get for "contributing" in some way.
But heck -- don't feel bad -- I've been hanging around here for YEARS and was here for a good long while before the software upgrade 2 years ago -- and ..... I only just figured out the green line thing about a month ago!! LOL