The Deutsche Marine (German Navy) uses a relatively dark grey compared to most other modern navies.
The translation by "Guest" is correct.
Some photos of Bremen class frigates to show how different the colours appear in different light conditions (click on the linked pages on "Link zur Bildergalerie" to see the photos):
Lübeck 2019Karlsruhe 2012Karlsruhe 2015Karlsruhe 2016Augsburg 2019Rheinland-Pfalz and Augsburg 2007These photos show a lot of differences compared to the NNT kit, which depicts an early fit of the class.
P.S. the ship was called Köln, not Koln.