Hi,
You have two types of custom fields:
1 the custom fields where you configure values in them and you can select one or several values in the element (dropdown, checkbox, radio, etc)
2 the custom fields which let you enter a value directly in the element (text, text area, etc)
Until recently, only the type 1 custom fields were translatable. To do so, it's easy. Instead of enter the text in one language in the "title" field of each value of the custom field, you need to enter a translation key of your choosing. For example, you can enter NOIR there.
Then, in the translation override (you can access the text area to edit it at the bottom of the popup of the language file translation, under the "languages" tab of the HikaShop configuration), you can add such line:
NOIR="Black"
or:
NOIR="Noir"
(for each language file).
That way it's easy to translate them:
you translate the values once, and then you only have to select the value once in the element. When the custom field is displayed, it will automatically display the translated title to the user.
In fact, you don't even need Falang to translate these custom fields since it uses the language file system of Joomla.
For the type 2 custom fields, we've added last year a "translatable" setting so that you can translate the value you enter in each element. So it's more work, but you have more flexibility. This method requires Falang.