Ryan,
The marks are white because some folks like to make the markings stand out so it's easier to read them. Some think it looks good, others think it looks lousy. The only marking that should have white color is the safety marking gesichert.
Folks use different substances to whiten the markings: chalk, grease pencils,paint, or brownells has what is called a laquer stik
http://www.brownells.com/aspx/NS/sto...spx?p=7778&s=.
Hope this answers your question.
Tom