The shade used in the grout of tuff_bricks.png at (0,7) (assuming the top-left pixel is (0,0) and becomes positive going down and right, similar to block UV) and throughout the rest of the texture is not the same as a similar shade of grout throughout the rest of the tuff blockset (except tuff, which does not have a consistent palette with the rest of the tuff blockset).
For reference, the shade used throughout tuff_bricks.png is hex code #434a3d while the shade used in the rest is #454a42. Very similar, but not quite the same, which is likely an oversight.

This can be remedied in two ways:

1. Replace every instance of #454a42 in the tuff blockset with #434a3d
2. Do the opposite, being replacing every instance of #434a3d in the tuff blockset with #454a42
   Personally I believe approach #2 should be taken, as it affects the least amount of textures, being tuff_bricks.png and nothing else.

In the image attached, arrows point to examples of the inconsistent colors being used, as well as the hex code of each. Do note that the shade found in polished tuff appears in every other tuff blockset block besides chiseled_tuff_bricks_top.png, as it doesn't have either.