Black iron sights are still the fastest for those of us with healthy eyes and excellent visual activity. Here's why...
Human eyes have two primary receptor cells--cones and rods.
The cones, working with the brain, perceive color.
The rods, working with the brain, discern contrast, shadow, and movement.
In the fear-threat mode, the human eye-brain sees contrast, shadow and movement, faster than anything else; this includes our peripheral vision.
In low light, the human eye-brain sees the contrast, shadow, and movement components of vision, first and best.
By faster, we're talking fractions of seconds. But when we're talking survival and serious competition, those fractions of seconds can make all the difference!
Still, black iron sights are of little use in near darkness…
Enter tritium night sights! The tritium-charged lamps stimulate the cones in the eyes and allow targeting in near total darkness. They're also passive, in that they won't necessarily reveal your position.
Likewise, fiber optic sights stimulate the cone cells, and while they're a bit
slower than iron sights in ample light (with a sharp-eyed shooter), they're a great overall solution for the rest of us!
If you really want to score hits in near darkness, get a laser!