Famously Colt Firearms has always offered private edition guns made to the customers specs as far as cosmetics like engraving, custom grips, gold or silver inlays, barrel length, etc are concerned.
Colt will pretty much make whatever the buyer can pay for, the skies the limit.
Colt will make special order individual guns for a single buyer, or private edition models.
At one time there was a 25 gun minimum for a private edition. I don't know about now, but I think there is no longer a minimum order.
These private editions are made for fraternal and police organizations, companies as employee or customer gifts, for sales as money raisers for organizations, and for people who just want to give friends a unique gift.
Since these are private issue sales, most are unknown to Colt collectors.