Try how the subtitles look if you change:
to
in the idx file.
Cu Selur
Ps.: instead of 'ffffff' (= 255/255/255) you could also try 'ebebeb' (=235/235/235)
palette: 101010, 101010, 101010, 101010, 101010, 101010, 101010, 101010, 101010, 101010, 101010, 101010, 101010, 838383, bfbfbf, 101010
palette: 000000, 000000, 000000, 000000, 000000, 000000, 000000, 000000, 000000, 000000, 000000, 000000, 000000, bfbfbf, ffffff, 000000
Cu Selur
Ps.: instead of 'ffffff' (= 255/255/255) you could also try 'ebebeb' (=235/235/235)