Why did the community give up the ability to see color in The Giver?
Jonas's community is founded on the principles of Sameness, which champion uniformity, comfort, and obedience. In Jonas's community, sunshine, colors, music, and personal choice do not exist. In the distant past, a decision was made to eliminate all differences and create a completely uniform, regimented society, where everybody conforms in order to have a safe, comfortable community. Sameness was the outcome of this decision and Jonas grows up in a mundane society, where everyone is required to adhere to strict standards and contribute to the community as a whole.
After Jonas is selected to be the community's Receiver of Memory, he begins is his training sessions and experiences life before Sameness, where humans had opportunities, personal freedoms, and enjoyed the spontaneity of life as originally intended.
Since Jonas has the Capacity to See Beyond, he has the unique ability to see in color and asks the Giver why the committee eliminated colors. The Giver responds by telling Jonas that the committee relinquished sunshine and did away with color to prevent differences. The committee's primary goal was to create a comfortable, safe society, which would stand the test of time.
In order to prevent conflict, the committee commissioned scientists to eliminate sunshine and color. Without color, people share a similar perspective and differences no longer exist. Since conflict stems from differences, the committee felt that these restrictions would benefit society as a whole and ensure its stability.