The Diff files read as follows. The one line which has a line number scratched out is the old code and line number. The new code corresponds to what the line number will be with the modification. All the other changes in the diff file that far down should not be too hard to spot. Look closely right around and compare the lines numbers. Beyond Compare is the best if your not using it.
The CSS additions you are correct get done to ALL stylesheets. You need to set the colors on the classes as instructed. After you cut and paste you need to replace DARKTABLE with the darktable color etc and do this for every new class converting to what color it is going to be. This is usually the longest step in this hack as I have over 25 stylesheets.
