In the old days guys used to paint their front sight a loud color to help it stand out. Somewhere along the line somebody thought of putting a small gold insert in the front sight and buffing it to a high shine so that it would be more visible in low light.
Today practically every maker out there offers a weapon with tritium sights pre-installed from the factory. While this is a good thing, unfortunately the dominant sight configuration is to have three “dots”, each with a tritium vial in it that is the same size, color, and brightness. This, as it turns out, isn't an ideal setup.
When you look through the sights of a handgun, the rear sight appears to be bigger than the front sight of the handgun. This is because it is closer to your face.
In low light with tritium sights that are all the same color and brightness when side by side, the rear sights are actually going to appear to be bigger and BRIGHTER than the front sight, making it harder to find and focus on the front sight under stress.
Thankfully there are sight makers who have realized this and who offer sights in various color combinations to try and help a shooter to distinguish between the front and rear sights under stress.