Where does “sötétkék” come from?

sötétkék (Hungarian) comes from Hungarian sötét, from Proto-Ugric čettɜ- — to become dark.

sötétkék (Hungarian): dark blue

Definitions

Step	Language	Word	Meaning
1	Hungarian	sötét	dark, sombre , somber; unintelligent, stupid,...
2	Proto-Ugric	čettɜ-	to become dark

sötétkék — Etymology, Origin & Word History | Etymology Explorer