The word(s) "dark" appears 46 time(s) in 43 verse(s) in Quran in Abdullah Yusuf Ali translation.

(21) When news is brought to one of them, of (the birth of) a female (child), his face darkens, and he is filled with inward grief!

(22) Establish regular prayers - at the sun's decline till the darkness of the night, and the morning prayer and reading: for the prayer and reading in the morning carry their testimony.

(23) And remember Zun-nun, when he departed in wrath: He imagined that We had no power over him! But he cried through the deptHs of darkness, "There is no god but thou: glory to thee: I was indeed wrong!"

(24) Or (the Unbelievers' state) is like the depths of darkness in a vast deep ocean, overwhelmed with billow topped by billow, topped by (dark) clouds: depths of darkness, one above another: if a man stretches out his hands, he can hardly see it! for any to whom Allah giveth not light, there is no light!

(25) Or, Who guides you through the depths of darkness on land and sea, and Who sends the winds as heralds of glad tidings, going before His Mercy? (Can there be another) god besides Allah?- High is Allah above what they associate with Him!

(26) He it is Who sends blessings on you, as do His angels, that He may bring you out from the depths of darkness into Light: and He is Full of Mercy to the Believers.

(27) Nor are the depths of darkness and the Light;

(28) And if they reject thee, so did their predecessors, to whom came their messengers with Clear Signs, Books of dark prophecies, and the Book of Enlightenment.

(29) And a Sign for them is the Night: We withdraw therefrom the Day, and behold they are plunged in darkness;

(30) Yea, such! - then shall they taste it,- a boiling fluid, and a fluid dark, murky, intensely cold!-