hinata shoyou (日向 翔陽)
陽 connotes "yang" or the positive, sun/day

kageyama tobio (影山 飛雄)
影 (pronounced "kage") is interchangeable with 陰 (also pronounced "kage", which connotes yin or the negative, shadow/dark

yang is associated with white/light, while yin is associated with black/dark...

their journey has them start in their respective colors, but we end with them switched!!

essentially...hinata and kageyamas journey in the manga is one of a repeating cycle. there is no yin without yang, and there is no yang without yin...they coexist and strive for balance.

the best illustration of this cyclic movement is with the volume 24 and 25 covers

furudate notes in the artbook;
Hinata in the "night"
Kageyama waits for "morning"

what does that mean?

this part of the story is right in the middle, its 208-224. thus, its in the middle of the cycle. they are moving clockwise...

hinata in the "night"
kageyama waits for "morning"

(note...there is an amazing thread in jpn about this, which is where i got the illustration of the movement from)

in addition to this...their story is one that is about striving for balance, and doing that through one another.

tobi has written a nice thread about this https://twitter.com/tobioshollow/status/1273377946997272576