Th .45 Colt may also be properly referred to as the .45 Long Colt.
Gunwriters have referred to the cartridge as the .45 Long Colt.
Reloading manuals have referred to the cartridge as the .45 Long Colt.
The United States government referred to the cartridge as the .45 Long Colt.
Frankford Arsenal referred to it as the .45 Long Colt.
Colt produced boxed ammunition labeled as .45 Long Colt.
And, most importantly, I like to refer to it as the .45 Long Colt...which should make it official...