How to customize windows frames (panels)

I want to learn to customize GTK themes. So far I have managed to learn how to change the background (accent) цвет, text цвет и т.д...

I хан change colors by changing the оценил in the поля in/usr/share/themes//gtk-3.0/gtk.css. By changing оцени in this code I хан play with the colors.

/* default color scheme */

@define-color bg_color #cdc3b8;
@define-color fg_color #262626;
@define-color base_color #accdff;
@define-color text_color #262626;
@define-color selected_bg_color #01b9fc;
@define-color selected_fg_color #ffffff;
@define-color tooltip_bg_color #A3D0FF;
@define-color tooltip_fg_color #023C79;

But where exactly in the theme пахал the поля for the windows frames (panels) so I хан change text of the tittlebar, change цвет of the frames? If possible would really be helpful if you also say what code is for what purpose.

Tthank you.