Taken from Michael Kasmar's upcoming Book On Autographs:
Blue has always been the preference on photos because even in dark areas it tends to POP a little more but over the years celebrities have been shying away from using blue markers. Part of it was from a rumor that I think dates back to Beyonce who said there were people using blue signatures to reproduce them on other items but more recently says people are “bootleggin” when they use blue and it’s just become a symbol of what all eBay sellers used so several celebrities treat it like a virus. Some celebrities who are definitely anti-blue include Red Hot Chili Peppers Flea, Aerosmith Steven Tyler, Slash’s security calls your items eBay if he sees blue, Joan Baez, Jake Gyllenhall, and the list really goes on so always have black as a backup and don’t even try these names with blue.

Michael Kasmar
www.AutographPros.com