Yes, and the black spat buttons were not adopted in isolation but as part of a suite of additions of black to the uniform (not all of which occured at the same time)

-black spat buttons
-a strand of black cord interwoven with the gold cord of officers' epaulettes (this could still be seen with the officers' uniforms of The Highlanders until the creation of the RRS)
-a black line in the centre of the gold lace on officers' jackets
-black and red hose (as opposed to the orginal white and red hose; this change didn't occur until c1860)
-and possibly unrelated, but ORs of the Gordon Highlanders wore black sporrans until the 1880s when white sporrans were adopted

Also, the spats of the old Gordon Highlanders were taller than hose of the other kilted regiments... yet another of the many subtle ways that the uniform varied from regiment to regiment in the old days.