I, for one, am not so convinced this is true for a 45, necessarily. First off, choose low flash loads... SEcondly, how long does it take to blink versus how long the flash hangs in the air?
I will certainly conceed the fact that "low flash" has no industry standard of measure. And I'll also conceed that you can find pictures of muzzle flash. But does the flash hang longer then it takes for you to blink? Do you not blink as the pistol 2 to 3 feet from your eyes fires?
Yes, if you choose slower burning powders, or loads containing slower burning powders, you will see the flash in many calibers, but I'm not so sure any decent 45ACP load will do that.
Now, a full house 44 magnum and Alliant 2400 power makes one heck of a visable flash, as it hangs due to the slow burn and the fact that the burn generally takes longer than the bullet is in the barrel. It's half flame thrower in many cases.
But be sure that I'm not one to say to port a defense pistol. Race guns? Fun guns? Yes to both, but not something I may have to shoot from my armpit, just as soon as it clears a holster.