Single Selection and Multi-Selection fields contain values which are predefined in Composer. When there are multiple locales in use, these values can be translated in different languages.
Resolution
Go to Application Administrator > More > Localization
Make sure "Allow Translation for MLS Runtime Objects and Design Objects" is enabled. If it isn't enabled, proceed to step 3, otherwise proceed to step 5.
Enable "Allow Translation for MLS Runtime Objects and Design Objects"
(Re)Deploy the process app where the fields are defined. This will add the elements to Localization Values
Go to Values > [App Name] > Selection
Look through the list of values, and select the one that needs to be translated.
Use the "Add" button to create a new copy of the value in the desired language
Additional Information
One language/locale may have multiple sub-options - e.g. Spanish may have "Spanish", "Spanish (Argentina)", "Spanish (Mexico)", etc. All these need to be translated separately depending on what locales will be used in the system. A users current locale can be found in their Profile Settings, on the Locale page.
The feature depends on the "Allow Translation for MLS Runtime Objects and Design Objects" setting being enabled. Therefore, if applications are deployed while the setting was disabled, their values won't be available for translation. Once the setting is enabled, all the applications to be translated will need to be re-deployed in order for the values to appear in Application Administration > Localization