Couple things:
How you hunt them depends in part upon whether it's spring or fall. Mating season is typically tom only, and you can use their mating calls against them (mating yelps, tom gobbles, cutting). Fall may be tom only or either sex, depending on where you live, and calling them is more difficult (helps to know the more advanced calls like kiki-run and assembly in the fall, but basic soft clucks and purrs always help). Really, you just need to "find them" - find where they are walking around and where they are roosting (using tracks, scratched ground & leaves, and their droppings). They will follow the same pattern until it is disturbed, ordinarily.
While they do recognize color, they are NOT necessarily alarmed by it. They are used to seeing wildflowers, trash, and other items containing color, and I've had them come right up to me wearing blaze orange - you just have to be still - they spot movement very well indeed. I think they are slightly better than deer at spotting slight movements, but actually slightly LESS astute than deer at making out your still outline as being human/danger.
20 ga or 12 ga (3" or 2.75" doesn't matter, but a heavy load, high brass), with 4, 5, or 6 shot, pattern your shotgun and shoot for the head & neck area - aim for the neck just immediately below the head. Get them within 35 yards first; preferably less than 20.
Wear orange in and orange out. You can take off the orange after you're set up.
If the turkeys are coming your way, STOP CALLING - let them come in and not pinpoint you exactly. Only keep/resume calling if they start walking away or are still far away (more than 60-70 yards).