Datacolor User to User Support Group.

> Also somebody mentioned silver paint for the tip (or white paint), 
> where would one find that in a handy form to apply.  I have a 
> terrible time seeing the outline of the tip on a dark patch.
> Jack Winberg

I use a white china marker as it's not permanent.

Any good stationary/art store will have silver metallic pens...I just did a search and Sharpie 
has them:

http://www.answers.com/topic/silver-ink-pen-or-marker