In chapter 3, Lily points out that the newchild, who becomes known as Gabriel, has "funny eyes" like Jonas. In fact, these eyes are the first thing Jonas notices about the infant.
Almost everyone in the community has dark eyes; their physical features have been genetically modified over time to be increasingly similar to everyone else. Both of Jonas's parents have dark eyes (though he is not genetically related to them, as it is later revealed), and so does his sister, Lily. It is odd to find a person with "light," which are blue, eyes.
As it turns out, people with blue eyes are the only ones who can see in color or who can share and receive memories. The Giver also has blue eyes, as does another young female child in the community whom Jonas has seen before. It is considered rude in their society to point out the differences which make individuals unique, so Jonas has never before commented on the light-colored eyes around the community which are so similar to his own. Yet in this moment of meeting Gabriel, Jonas feels the connection between them, their similarities drawing Jonas to this child who is in need of additional nurturing. This initial bond will continue to develop over time as Jonas learns more about the various truths of their society.