I think contrast is a good thing. You have enough dark things in your space to keep the black grills. Looking at the first pic, if you go to a lighter grill it will look too much like the vertical logs of the fireplace. If you can, drape the swatches over the top of the speakers so they can partly hang down the front, and then look at them. If you want the speakers to blend in with the wall, that's ok, but for my money I'd stick with black, or one of the darker colors.

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose