Why were Gabe’s eyes of such interest to Jonas in The Giver?

Gabe has the same pale eyes as Jonas.

Jonas is attracted to Gabe’s eyes because they are light-colored, like his own.  Almost no one else in the community has pale eyes.  Sameness is crucial to Jonas’s community, and part of the Sameness employed means that everyone to have the same eye color.  No one sees color, but they are aware that some eyes are lighter than others.

Jonas feels subconscious about his eye color.  It is considered rude for anyone in the community to call attention to it, but his younger sister does.

"Oh, look!" Lily squealed in delight. "Isn't he cute? Look how tiny he is! And he has funny eyes like yours, Jonas!" Jonas glared at her. He didn't like it that she had mentioned his eyes. (Ch. 3)

After looking into baby Gabe’s eyes, Jonas notices that the eyes give the baby a deep look, as if he knows things others do not.  Jonas realizes that his eyes have the same effect on people.  It is unsettling, and adds to the fact that Jonas seems different.

Now, seeing the newchild and its expression, he was reminded that the light eyes were not only a rarity but gave the one who had them a certain look--what was it? Depth, he decided … He felt self-conscious, realizing that he, too, had that look. (Ch. 3)

Jonas does not realize how different he is until he is chosen Receiver of Memory.  This job is a special honor, and an assignment only given rarely.  The current Receiver of Memory has the same pale eyes Jonas has. 

It turns out that Jonas, The Receiver, and Gabe are all genetically related.  The eyes are significant because they pass on a rare trait that allows the individual to access memories.  For Jonas, this is called the Capacity to See Beyond.  It also means that he can see color when no one else can, after he has accessed enough memories.

Jonas is drawn to Gabriel.  He has the baby moved to his room when he fusses, so that he can comfort him himself.  One day when he is rubbing the boy’s back he accidentally transmits a memory to him.  This is when Jonas realizes just how special Gabe truly is.  Like The Giver and Jonas, Gabe can access the memories.  He has the Capacity to See Beyond.

The time spent on eye color and how rare it is early in the novel foreshadows Jonas's significance and his special ability.  It also foreshadows the role Gabe will play in Jonas's life.  As Jonas becomes more independent from his community through the memories, he gets drawn more and more to the special Gabe.  Everything about the baby is unique, from the way he ended up in Jonas's home to his ability to receive memories.  Jonas is very close to Gabe, and it is Gabe's impending release that forces Jonas to flee ahead of schedule.