[Решено] Цвет фона всплывающей подсказки

sudo apt install breeze
sudo apt install breeze-gtk-theme
sudo apt-mark auto breeze-gtk-theme

$ dpkg -l | grep breeze
ii  breeze                                                      4:5.12.8-0ubuntu0.1                                         amd64        Default Plasma theme (meta-package).
ii  breeze-cursor-theme                                         4:5.12.8-0ubuntu0.1                                         all          Default Plasma cursor theme.
ii  breeze-gtk-theme                                            5.12.8-0ubuntu0.1                                           amd64        GTK theme built to match KDE's Breeze
ii  breeze-icon-theme                                           4:5.44.0-0ubuntu1                                           all          Default Plasma icon theme.
ii  kde-style-breeze                                            4:5.12.8-0ubuntu0.1                                         amd64        Widget style for Qt and KDE Software
ii  kde-style-breeze-qt4                                        4:5.12.8-0ubuntu0.1                                         amd64        Widget style for Qt 4 and KDE Software
ii  kwin-style-breeze                                           4:5.12.8-0ubuntu0.1                                         amd64        KWin Breeze Style
ii  libreoffice-style-breeze                                    1:6.0.7-0ubuntu0.18.04.11                                   all          office productivity suite -- Breeze symbol style
ii  plasma-look-and-feel-org-kde-breezedark-desktop             4:5.12.8-0ubuntu0.1                                         all          Dark Breeze look-and-feel for Plasma
ii  qml-module-qtquick-controls-styles-breeze                   4:5.12.8-0ubuntu0.1                                         amd64        QtQuick style for Qt and KDE Software
ii  sddm-theme-breeze                                           4:5.12.6-0ubuntu0.1                                         amd64        Breeze SDDM theme

widget "gtk-tooltip" style "ToolTip"
widget "gtk-tooltips" style "ToolTip"

$ cat ~/.config/gtkrc-2.0
# created by KDE Plasma, чт сент. 6 00:06:33 2018
#
# If you do not want Plasma to override your GTK settings, select
# Colors in the System Settings and disable the checkbox
# "Apply colors to non-Qt applications"
#
#

gtk-alternative-button-order = 1

style "default"
{
  bg[NORMAL] = { 0.988, 0.988, 0.988 }
  bg[SELECTED] = { 0.239, 0.682, 0.914 }
  bg[INSENSITIVE] = { 0.988, 0.988, 0.988 }
  bg[ACTIVE] = { 0.890, 0.890, 0.890 }
  bg[PRELIGHT] = { 0.988, 0.988, 0.988 }

  base[NORMAL] = { 0.988, 0.988, 0.988 }
  base[SELECTED] = { 0.239, 0.682, 0.914 }
  base[INSENSITIVE] = { 0.988, 0.988, 0.988 }
  base[ACTIVE] = { 0.239, 0.682, 0.914 }
  base[PRELIGHT] = { 0.239, 0.682, 0.914 }

  text[NORMAL] = { 0.137, 0.149, 0.153 }
  text[SELECTED] = { 0.988, 0.988, 0.988 }
  text[INSENSITIVE] = { 0.890, 0.890, 0.890 }
  text[ACTIVE] = { 0.988, 0.988, 0.988 }
  text[PRELIGHT] = { 0.988, 0.988, 0.988 }

  fg[NORMAL] = { 0.137, 0.149, 0.153 }
  fg[SELECTED] = { 0.988, 0.988, 0.988 }
  fg[INSENSITIVE] = { 0.890, 0.890, 0.890 }
  fg[ACTIVE] = { 0.137, 0.149, 0.153 }
  fg[PRELIGHT] = { 0.137, 0.149, 0.153 }
}

class "*" style "default"

style "ToolTip"
{
  bg[NORMAL] = { 0.937, 0.922, 0.906 }
  base[NORMAL] = { 1.000, 1.000, 1.000 }
  text[NORMAL] = { 0.000, 0.000, 0.000 }
  fg[NORMAL] = { 0.000, 0.000, 0.000 }
}

#widget "gtk-tooltip" style "ToolTip"
#widget "gtk-tooltips" style "ToolTip"

style "MenuItem"
{
  bg[PRELIGHT] = { 0.239, 0.682, 0.914 }
  fg[PRELIGHT] = { 0.988, 0.988, 0.988 }
}

class "*MenuItem" style "MenuItem"