Lasers are of minimal use as a sighting technology, folks tend to loose focus chasing the dot and their aim actually suffers as a result. BUT they are excellent training tools. Get some snap caps, and a target the size of a silver dollar, or lid of a small jar, playing card etc you can start larger and work to smaller and smaller targets. Put it 10+ feet away. With the weapon cleared and chambered with snap caps. Turn on the laser and with slow careful movements put the laser on target and with the chambered snap caps, slowly pull the trigger 10 times holding the laser on target the entire time. Do not be terribly surprised if you see the laser going all over hell and gone the first couple times you try this. Turn off the laser. Rest for 30 seconds plus then repeat with the laser off but keeping your iron sights on the target. Repeat at least 3-4 times per session. Do this twice a day, inside a week you will see significant tightening of your groups shooting, due to the training feedback on the laser and helping build muscle memory for proper grip. In a couple weeks you will get down to aiming at light switch plates and holding sights/laser steady on the tip of the switch. When you have your grip trained in like this add sessions , going from snap point, and draw to proper hold and on target holding the laser on target through the drill.
With this training you will find you can actually use the laser tactically, but to be honest to me it is more a light on the target with target intimidation as a bonus than an actual sight, even when I use the laser I still mainly work the iron sights. So with snap caps and appropriate care when training they are a great training tool, they have a great intimidation factor on a target (though the first thing the target should see is the muzzle flash) but I don't advocate them as a primary sight.
That said green lasers are better than red lasers for either application. Visible in full daylight, and blinding to the target at night