Here's a post I recently made on the subject of Sam Colt being left-handed.
"...there is no evidence that Sam Colt was left handed or that that was the reason for the layout of the sixgun. The revolver, at that point in time, was a secondary cavalry weapon. It was worn butt forward, on the right hip so that it could be drawn with either hand but it was meant to be used with the left hand. The saber was the primary weapon and it was always worn on the left side. Colt designed a cutout in the right side of the frame of his percussion guns for capping. This was so that the sixgun could be held in the left hand while the dominant right hand could be used for operating the powder flask, ramming balls and capping. This was carried over, years after Sam Colt's death, when Charles Richards and William Mason designed cartridge conversions on the percussion pistols and their 1872 Open Top successor. This was Colt's first dedicated metallic cartridge sixgun chambered in .44 rimfire. It was submitted to the Army for testing. It was rejected, as they wanted a centerfire .45 caliber cartridge and a solid frame. THE ARMY is responsible for those two major changes that ultimately led to William Mason's design of the 1873 Single Action Army in late 1872. If it would've been better for a predominately right-handed cavalryman to have the loading gate on the left side, don't you think the Army would've ordered it that way?
It's worthy of note that the loading gate/capping cutout on Remington percussion and cartridge sixguns is also on the right side.
I, for one, do not believe Bill Grover's design to be better for right-handed shooters and most veteran sixgunners agree. You can operate a single action much more quickly and efficiently by changing it over to the left hand, turning the cylinder with the left thumb and forefinger while operating the ejector with the right thumb or forefinger. I then transition to the right hand to load with the left. I shoot 20-30,000rds a year through single actions and have found this to be the most efficient way to reload a single action. Usually takes 12-15 seconds to unload and reload in this manner."