/usr/share/themes/Xfce-basic/gtk-2.0/gtkrc is in gtk2-engines-xfce 3.2.0-2.
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 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 | style "default"
{
    GtkButton::default_border         = {0, 0, 0, 0}
    GtkButton::default_outside_border = {0, 0, 0, 0}
    GtkButton::default_spacing        = 8
    GtkButton::focus-line-width       = 1
    GtkButton::focus-padding          = 2
    GtkMenuBar::shadow_type           = out
    GtkPaned::handle_full_size        = 1
    GtkToolbar::shadow_type           = out
    GtkWidget::interior_focus         = 1
    GtkRange::slider_width            = 14
    GtkRange::stepper_size            = 14
    GtkRange::stepper_spacing         = 0
    GtkRange::trough_border           = 0
    fg[ACTIVE]        = "#000000"
    fg[INSENSITIVE]   = "#757575"
    fg[NORMAL]        = "#000000"
    fg[PRELIGHT]      = "#000000"
    fg[SELECTED]      = "#ffffff"
    bg[ACTIVE]        = "#c4c2bd"
    bg[INSENSITIVE]   = "#dcdad5"
    bg[NORMAL]        = "#dcdad5"
    bg[PRELIGHT]      = "#eeebe7"
    bg[SELECTED]      = "#4b6983"
    base[ACTIVE]      = "#9c9a94"
    base[INSENSITIVE] = "#eeebe7"
    base[NORMAL]      = "#ffffff"
    base[PRELIGHT]    = "#ffffff"
    base[SELECTED]    = "#4b6983"
    text[ACTIVE]      = "#ffffff"
    text[INSENSITIVE] = "#757575"
    text[NORMAL]      = "#000000"
    text[PRELIGHT]    = "#000000"
    text[SELECTED]    = "#ffffff"
    engine "xfce" 
    {
        smooth_edge = true
        grip_style = none
        boxfill
        {
            fill_style = plain
        }
    }
}
widget_class "*"                style "default"
style "button" = "default"
{
    xthickness = 2
    ythickness = 2
    engine "xfce" 
    {
        smooth_edge = true
        grip_style = none
        boxfill
        {
            fill_style = gradient
            orientation = vertical
            shade_start = 1.10
            shade_end = 1.00
        }
    }
}
widget_class "*Button*"            style "button"
class "*Button*"                   style "button"
# This is for ROX-Filer
# 
style "rox" = "default"
{
  bg[NORMAL] = "#ffffff"
  bg[ACTIVE] = "#ffffff"
}
widget_class "*Collection"         style "rox"
style "scrollbar" = "default"
{
    xthickness = 2
    ythickness = 2
    engine "xfce" 
    {
        smooth_edge = true
        grip_style = none
        boxfill
        {
            fill_style = plain
        }
    }
}
widget_class "*Scrollbar*"         style "scrollbar"
class "*Scrollbar*"                style "scrollbar"
widget_class "*GtkScale*"          style "scrollbar"
class "*GtkScale*"                 style "scrollbar"
 |