Should a blue or black ballpoint pen be used to get baseballs autographed and what is the difference?

Since it is hard to photocopy blue, blue is a better color to prove authenticity In the case of a baseball Blue ball point pen has proven to hold up better over time, and would be most preferred over sharpie which tends to fade quicker. A sharpie signed baseball will also tend to "bleed" into the baseball as well. An educated collector will pay less for a sharpie signed baseball, if at all. Sharpie would be most preferred on a bat, or Photo. As far as Blue ball point over Black. I can't tell you why but this is what the "experts" recommend. My guess would be different chemicals are used to make different colored ink, and the blue holds up better. If you notice all top companies that do mass private signings like upper deck, Steiner Sports, Iron Clad Authentic etc. All use Blue ball point pens on baseballs (not Black) there must be something to it.