changed the whole GTK3 part

usr/share/themes/Lubuntu-default/gtk-3.0/gtk.css

@@ -4,63 +4,37 @@
 @define-color bg_color #e0e0e0;
 @define-color fg_color #333;
 @define-color base_color #fff;
-@define-color text_color #333333;
+@define-color text_color #333;
 @define-color selected_bg_color #8FB2CF;
 @define-color selected_fg_color #fff;
 @define-color tooltip_bg_color #333;
 @define-color tooltip_fg_color #fff;
 
 /* misc colors used by gtk+ */
-@define-color link_color #3168A0;
-@define-color warning_color #f57900;
+@define-color info_fg_color rgb (181, 171, 156);
+@define-color info_bg_color rgb (252, 252, 189);
+@define-color warning_fg_color rgb (173, 120, 41);
+@define-color warning_bg_color rgb (250, 173, 61);
+@define-color question_fg_color rgb (97, 122, 214);
+@define-color question_bg_color rgb (138, 173, 212);
+@define-color error_fg_color rgb (166, 38, 38);
+@define-color error_bg_color rgb (237, 54, 54);
+@define-color link_color #4a90d9;
 @define-color error_color #cc0000;
-@define-color success_color #4e9a06;
 
 /* theme common colors */
 @define-color button_bg_color shade (@bg_color,1.02);
 @define-color button_insensitive_bg_color mix (@button_bg_color, @bg_color, 0.6);
+@define-color dark_bg_color @bg_color;
+@define-color dark_fg_color @fg_color;
 @define-color transparent rgba (0, 0, 0, 0);
+@define-color backdrop_selected_bg_color shade (@bg_color, 0.92);
+@define-color backdrop_selected_fg_color @fg_color;
 
-@define-color internal_element_color #afafaf;
-@define-color insensitive_bg_color #f5f5f5;
-@define-color insensitive_fg_color #a7a7a7;
-@define-color insensitive_border_color shade (@internal_element_color, 1.37);
-@define-color inactive_frame_color #c8c8c8;
-@define-color inactive_frame_border_a #8b8b8b;
-@define-color inactive_frame_border_b #c6c6c6;
-
-@define-color trough_bg_color_a #e0e0e0;
-@define-color trough_bg_color_b #b9b9b9;
-
-@define-color toolbar_gradient_base #e0e0e0;
-@define-color toolbar_gradient_final #d0d0d0;
+@define-color toolbar_base #e0e0e0;
+@define-color toolbar_final #bcbcbc;
 @define-color toolbar_border #fff;
 
-@define-color button_gradient_color_a shade (@button_bg_color,1.1);
-@define-color button_gradient_color_b shade (@button_bg_color,0.95);
-@define-color button_hover_gradient_color_a mix (@bg_color, shade (@selected_bg_color,1.4),0.7);
-@define-color button_hover_gradient_color_b mix (@bg_color, shade (@selected_bg_color,1.25),0.5);
-@define-color button_active_gradient_color_a shade (@button_gradient_color_b, 0.80);
-@define-color button_active_gradient_color_b shade (@button_gradient_color_a, 0.80);
-
-@define-color progressbar_through_a #B7D1E6;
-@define-color progressbar_through_b #7BA2C3;
-@define-color progressbar_through_border #d0d0d0;
-@define-color progressbar_background_a #B7D1E6;
-@define-color progressbar_background_b #7BA2C3;
-@define-color progressbar_border #6594E6;
-
-@define-color menuitem_background_a #8ba4b8;
-@define-color menuitem_background_b #7a94a9;
-
-@define-color border_color_a #afafaf;
-@define-color border_color_b #7a7a7a;
-@define-color scrollslider_gradient_a #d8d8d8;
-@define-color scrollslider_gradient_b #bdbdbd;
-@define-color scrollslider_border #9a9a9a;
-@define-color listview_header_gradient_a #ececec;
-@define-color listview_header_gradient_b #d8d8d8;
-@define-color listview_border #cbcbcb;
-@define-color sidebar_color mix (@bg_color,shade (@selected_bg_color,1.35),0.8);
-
 @import url("gtk-widgets.css");
+@import url("gtk-widgets-backdrop.css");
+

usr/share/themes/Lubuntu-default/gtk-3.0/settings.ini

@@ -1,3 +1,3 @@
 [Settings]
+gtk-color-scheme = "base_color:#ffffff\nbg_color:#dcdcdc\ntooltip_bg_color:#000000\nselected_bg_color:#f07746\ntext_color:#3C3C3C\nfg_color:#4c4c4c\ntooltip_fg_color:#ffffff\nselected_fg_color:#ffffff\nlink_color:#DD4814\nbg_color_dark:#3c3b37\nfg_color_dark:#dfdbd2"
 gtk-auto-mnemonics = 1
-gtk-color-scheme = "base_color:#f7f7f7\nbg_color:#dcdcdc\ntooltip_bg_color:#F5F5B5\nselected_bg_color:#a2b8ca\ntext_color:#2c2c2c\nfg_color:#2c2c2c\ntooltip_fg_color:#000000\nselected_fg_color:#F5F5F5\nlink_color:#DD4814\nbg_color_dark:#c9c9c9\nfg_color_dark:#2c2c2c"