I believe some bank robbers painted the tips of their guns orange once. Here's an article: http://johnrlott.blogspot.ca/2010/03...s-on-real.html
As for why some guns have orange tips. As far as I can tell it boils down to the manufacturers/suppliers. Some treat North America as a homogeneous market and give everyone orange tips, others make a distinction between US, Canada, and Mexico. however you should note that some suppliers are stateside. E1/Jag Precision gets OEM stuff from Asia then resells under their brand name and add value added stuff like RMA/warranty support service which a lot of clone manufacturers don't do. Also supposedly the E1 stuff is stripped down and redone better than how the OEM manufacturer sent it out as like relubing with slightly better lube and making sure seals are a little bit better, not sure if this is true though since there's a lot of misinformatoin and rumours floating around trying to promote/differentiate one companies stuff from another and justify their pricing.