/usr/share/themes/CleanIce-Dark/gtk-2.0/gtkrc is in gtk2-engines-cleanice 2.4.1-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 | # Edit these colors and fonts however you like, after cp'ing the file to
# another theme directory.
# CleanIce-Dark by Bastien Nocera <hadess@hadess.net>
# CleanIce GTK+ Theme 2001 Rodney Dawes <dobez@fnmail.com>
# Based on ThinIce GTK+ Engine by Tomas Ogren
# and Clean GTK+ Engine by dengen40@yahoo.com
style "default"
{
  # Normal
  #
  # All these items have the same value,
  # <owen> hadess: No. There are no variables in gtkrc currently.
  #
  bg[SELECTED] = "#685977"
  base[SELECTED] = "#685977"
  base[INSENSITIVE] = "#685977"
  base[ACTIVE] = "#685977"
  #
  fg[SELECTED] = "#ffffff"
  text[SELECTED] = "#ffffff"
  text[INSENSITIVE] = "#ffffff"
  text[ACTIVE] = "#ffffff"
  # Blackcurrant
  # bg[SELECTED] = "#0f142c"
  # fg[SELECTED] = "#ffffff"
  # Citrus
  # fg[SELECTED] = "#000000"
  # bg[SELECTED] = "#f7c700"
  # Crowberry
  # fg[SELECTED] = "#ffffff"
  # bg[SELECTED] = "#34426d"
  # Eggplant
  # fg[SELECTED] = "#ffffff"
  # bg[SELECTED] = "#62526f"
  # Jade
  # fg[SELECTED] = "#ffffff"
  # bg[SELECTED] = "#345d56"
  # Lime
  # fg[SELECTED] = "#000000"
  # bg[SELECTED] = "#bedc00"
  # PopCorn
  # fg[SELECTED] = "#000000"
  # bg[SELECTED] = "#d6c787"
  # Pumpkin
  # fg[SELECTED] = "#ffffff"
  # bg[SELECTED] = "#c8702f"
  bg[ACTIVE] = "#909090"
  fg[ACTIVE] = "#000000"
  bg[NORMAL] = "#a3a2a0"
  bg[PRELIGHT] = "#685977"
  fg[PRELIGHT] = "#ffffff"
  bg[INSENSITIVE] = "#a3a2a0"
  fg[NORMAL] = "#000000"
  base[NORMAL]          = "#dddddd"     # list item background
  engine "cleanice"
  {
  }
}
widget_class "*" style "default"
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