Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.

color_custom_theme in core/modules/color/color.module
Implements hook_custom_theme().
menu_get_custom_theme in core/includes/menu.inc
Gets the custom theme for the current page, if there is one.
menu_set_custom_theme in core/includes/menu.inc
Sets a custom theme for the current page, if there is one.
menu_test_custom_theme in core/modules/simpletest/tests/menu_test.module
Implement hook_custom_theme().
system_custom_theme in core/modules/system/system.module
Implements hook_custom_theme().
views_ui_custom_theme in core/modules/views_ui/views_ui.module
Impements hook_custom_theme()