You should have a paint code sticker in the front trunk. I think is located on the right side under one of the black panels. The paint code is also listed in the opstions sticker located under the front hood and a second copy should be in your maint. book.
Here is a list of Porsche colors & codes for years 97-04 from Yoseif's site.
http://www.whiteson.org/boxster/gallery/years.shtml
look here for touch up paints
http://www.paintscratch.com