Why don't they see colors in the book The Giver?

In The Giver, Jonas becomes aware that certain things begin to look different to him. For example, he notices a change in the appearance of an apple, in faces in the crowd at the Ceremony, and in Fiona's hair. When he asks The Giver about what he sees, The Giver explains that Jonas is beginning to see the color red. The Giver tests his theory and asks Jonas to look at the sled from a memory he previously shared with Jonas. Jonas sees that the sled is in fact red. However, instead of changing to red, it is just red. This is because the memory is from a time when color still existed.
The Giver explains to Jonas that color no longer exists because the community embraces the concept of "sameness." He says, "We gained control of many things. But we had to let go of others." Without differences such as color, choices are limited. When choices are limited, there is less room for error.