I have seen color pictures of Kilos with their upper sonar area painted in what appears to be silver or light gray but I also have seen color pictures of Kilos with their upper sonar areas blacked out (either by sensors) or just painted black.
www.hazegray.org
Search "Russian Navy" photo section on Kilos.
For what it's worth, in Providence, RI we have one of the last surviving Juliett class submarines. Assuming they have restored it accurately, you might be able to get a better idea of the color by looking at this vessel. It's probably a standard color.
www.saratogamuseum.org