(Aside from the advanced technology that they use such as climate control and removing colour) can it actually happen in real life? How realistic is the novel?
Jim Jones' supposedly idyllic community of Jonestown (in Guyana) lasted only a short time before he poisoned the members of the Peoples Temple Agricultural Project rather than allowing them to leave freely. Only a few people escaped alive, while more than 900 willingly--and not-so-willingly--drank poisoned Kool Aid dispersed by Jones, who chose to eat a bullet instead.
I think that a group of people would have to cut themselves off from society first by heading for the hills if they truly wanted to set up a society like this. The first people to settle would all have to be there by their own choice and adopt all of the laws, rules, and regulations that would support that type of lifestyle. Some would call this a type of cult activity, though. It would be difficult for them to maintain such a society without needing some support from the outside, such as: medicine, trade, technology. On the other hand, some societies liek those of the Amish people have survived because they choose to live a different way than modern society. Of course, there are many differences between the Amish people and the people in The Giver, but it is interesting to think about.
There have often been groups who have tried to totally control their people. This has sometimes extended to genetic control. For example, the Nazis tried to use Eugenics to create their own race. Even without advanced technology, you can control what people do enough to replicate much of the Samness.
There are aspects of the community that could be replicated, but there has never to my knowledge been any community that has tried to have that much control over people's lives. In particular, I think that it would be horribly difficult to get people to give up family ties in the way that the people of Jonas's community have.