Translation/Localization support

It depends on what you use for translations…
WPML for example allows you to translate theme_mods by adding a configuration file. More info can be seen on https://wpml.org/forums/topic/translate-data-from-get_theme_mod/ and https://wpml.org/documentation/support/language-configuration-files/

WordPress currently doesn’t provide a default method to translate these, so it’s up to the multilingual plugin you use.