green, kingfisher
翠 centers on a vivid blue-green color, like the feathers of a kingfisher. The bird meaning is a specific application of that same striking color.
kingfisher
jade (stone)
kingfisher (esp. the common kingfisher, Alcedo atthis)
emerald
crested kingfisher (Megaceryle lugubris)
Midoriya
the sense of being engulfed in a green, mountainous atmosphere
approx. 80% of the way up a mountainside
Suimeiso (hotel and restaurant chain - suimeiso.co.jp)
verdant pine; green pine
green (esp. of trees, rocks, etc.)
green (of lush vegetation); verdure
dioptase
green eyebrow pencil; green-shaded eyebrows
jade green
blue-green
ruddy kingfisher (Halcyon coromanda)
翠 combines 羽 (feathers) with 卒, which likely contributes the sound. The character originally referred to the kingfisher's blue-green plumage.
Feathers 羽 on top of a soldier 卒: imagine a soldier wearing a helmet adorned with brilliant kingfisher feathers, the vivid green standing out against the armor.
For スイ, picture a kingfisher diving into a Swiss lake: Swiss -> スイ, and the bird's green feathers flash in the water.