Sean;
German WWII "dunkelgrau" (RAL 7021), the standard base (and only one authorized for European theater use through 1942) color used on all German AFV and other military vehicles, big guns, etc. per regulations from Aug 1940 was a dark gray with slight bluish or greenish tint (depending on one's color vision and interpretation!

). It was NOT a simple mix of black and white (i.e., a "neutral gray"), so cannot realistically be represented by any straight "gray" created along that simple gray scale.
How dark was it? That Q has been up, down, and all-around on modeling sites for years! Suffice to say that folks have argued for it being anywhere from "almost black" to something substantially lighter than most model-paint colors offered to represent this essential German color. And I'll stay well clear of the complicated "scale-effect" discussions, Thank You!
I personally find the Tamiya XF-63 "acrylic" pretty nice as a base right from the bottle. I sometimes add in a small amount of light deck-tan or white plus "dark yellow" to lighten it just a little bit, when doing some post-shading and variation on the coat to show some fading.
I also find the Testor's ModelMaster #2094 "schwartzgrau 1939 - 43" matt enamel to be pretty pleasing. Again, I sometimes add in some buff or white to lighten things a tad.
Each of these colors offers an interpretation of the tinted dark gray.
I generally apply these over a very dark Floquil "weathered black" or "engine black" pre-shade & primer coat. As it's dark gray over "black", things can indeed come off being a little dark, but my weathering goes heavily to light dust and "earth" shading, so...
See the below Pz 38(t) E/F painted using the Tamiya XF-63 with very little add-in applied over the Floquil weathered black and fairly heavily "dusted" with first a light over-spray of Tamiya flat earth to hi-light dirtier areas and later a bit of light artist's chalks applied as real dust.
Note that what we see HERE in this pic differs from what we see in other light and with other back-grounds. Take a look at this tank in the Track-Link galleries to see...
Maybe the points being, what you applied as the base (dunkelgrau) may well get quite modified as you go along! And YOU want to be pleased with what you get, in the end!
Cheers!
Bob