What does this passage from "The Giver" tell us about Jonas? "Like the apple, the people in the crowd changed."

At first, this is an example of foreshadowing.  We do not fully understand the changes Jonas sees, because we have not been introduced to the fact that the people in Jonas's community cannot see colors.  Later, when Jonas is with the Giver, we learn that the "changes" Jonas observed were really flashes of color.  Jonas was able to see the brighter colors, particularly red, first.  But he didn't have the vocabulary to describe exactly what he saw, because he had never before been introduced to the concept of colors.

This tells us that Jonas is different from the others in his community.  He notices things that they do not notice.  Later on, when he is chosen to be the Receiver, he learns that it was differences like this that gave him that job in the first place.  His ability to "see beyond" is what set him apart from his peers and made him a proper candidate for the Receiver position.