Jet Black
Pitch Black
noun, の adjective
Lacquer black looks jet black, or pitch black. It's as black as black can be!
しっこく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
漆黒の闇に青い地球が浮かんでいた。
The earth appeared in the black darkness.