Appendix D X Options and Resources
You can customize some X-related aspects of Emacs behavior using X resources, as is usual for programs that use X.
When Emacs is compiled with GTK+ support, the appearance of various graphical widgets, such as the menu-bar, scroll-bar, and dialog boxes, is determined by GTK+ resources, which we will also describe. When Emacs is built without GTK+ support, the appearance of these widgets is determined by additional X resources.
On MS-Windows, you can customize some of the same aspects using the system registry (see The MS-Windows System Registry).