The book tells us that the decision to move to climate control removed most colors. Thereafter the ultimate decision was made to minimize as many differences as possible genetically, thus, very little variation in eye, skin, and hair color.
"We relinquished color when we relinquished sunshine and did away with difference."
Sameness became the overriding requirement of the Community members. People like Fiona were considered technically "imperfect" because of the maintenance of the bright red hair which, while invisible to most Community members, directly opposed the guidelines of Sameness. It is certainly a comment--as are the pale eyes of Jonas, Gabe, and the Giver--regarding the inability of individualism to disappear completely, no matter the circumstances.
The community in which Jonas lives in has a motive to perpetuate sameness and color is known as an obstacle. In our world, citizens have different skin tones, hair color, eye color, etc. which makes citizens have differences between each other. Colors are generated by light receptors within the eye that produce a thing called color. With climate control there is no sunlight, which means no color. Having different colors would lead to having different choices as well, such as buying a blue car, or a red car. This may seem like a choice but for some people it can lead to stress which is not something wanted in a perfect society
It allowed for too many choices which community leaders did not want to give to their people. If the people of their community had a choice in this, a choice in more risky topics may be given as well. Also, climate control took away color because you need sumlight to see light.