Soon, the other four friends began to use nicknames: the boys were called Aka (red) and Ao (blue); and the girls were Shiro (white) and Kuro (black.” But he remained Tsukuru. How great it would be, he often thought, if I had a color in my name too.
-- Narrator (Chapter 1 paragraph 16)

Importance: This is one of the first times the reader sees why the Tsukuru is referred to as “colorless.” The reader will soon learn that there are other reasons, but the names are very important in this culture and provide a basis for Tsukuru's image of himself.

Searching for the reason, or correcting a misunderstanding, was beyond me. I was simply and utterly in shock.
-- Tsukuru (Chapter 2 paragraph 43)

Importance: Tsukuru is talking to Sara and he's explaining how he felt after being shut out of the group. She wonders why he didn't question them in case it was a misunderstanding but his grief was so complete that...