GTK2 colours are no longer exported.
This is necessary in 2019 because most popular GTK2 themes (including Breeze GTK) primarily use pixmaps
which cannot respect these colours. This results in odd-looking mixtures of some widgets following the
colourscheme and some not.
See: [[ https://bugsfiles.kde.org/attachment.cgi?id=122870 | {F7539529} ]]