Total n00b question here... i am looking to make some changes to my bike and i was wondering if you guys could help me.... I see a bunch of bikes with what seems like a stripe of color that runs around the inside part of the bike's tires... is taht part of a rim that i would have to buy or is taht apart of the tires taht i would have to buy.,.. or (and this is what im hoping) is it just an accessory i can buy and apply to any tire/rim.... thanks in advance

It's usually a tape that goes on the rim, not the tyre.

Some also paint it on.

Here's an example:

http://www.tapeworks.com/Rimstripes/RimstripesHome.html

Try googling for rim stripes or rim tape.