Until the late 1980's 45 Colt was .454" diameter.
The reduction of bore size from .454" down to .451-452" began after WWII, with different makers doing it at different times (and some not at all, or not till several decades later). It was not a standardized thing.
The idea was to get better accuracy from people shooting .45ACP bullets, and it makes no difference at all to the .454" lead bullets loaded in the .45 Colt ammo. The big lead slugs squeeze down that small amount just fine.
IF you're asking about the lead alloy in ACP and Colt bullets, it can be the same or it can be different, depending on who made them. Very soft alloys sometimes don't perform well in semi auto pistols, but revolvers don't care.
IN general, bullets 230gr and under are intended for the ACP, 250-255gr is the standard .45 Colt weight. There is a degree of "overlap". Generally, bullets made for use in revolvers will have a crimp groove. Bullets made for semi autos may not. Again, there are variations.
Take a look in a reloading manual and see what is listed. That will give you a base idea of what bullets are intended for which.
Do come back with any additional questions, we're here to help.