Black and Light Gray here FWIW... 80/20 mix. If doing it again, I'd go either with white and a higher percentage or a more balanced mix of light gray and black.
I'd think the dark gray and black might just end blending to be a lighter black, at least that is what McM told me when I asked about those colors. Hence the reason I went light gray.
Good luck though as picking the colors is half the fun and you only have to please yourself.