When considering using Garnier Black Naturals hair color on your moustache, it's important to keep a few things in mind:

• Product Intended Use: This hair dye is formulated for scalp hair, which is generally thicker and less sensitive than facial hair.

• Skin Sensitivity: The skin on your face, especially around the moustache area, is more sensitive and prone to irritation or allergic reactions compared to the scalp.

• Patch Test: Always perform a patch test 48 hours before applying the dye to check for any allergic reactions.

• Application Caution: Avoid contact with eyes and mucous membranes. Use carefully to prevent staining of the skin.

• Consultation: If you have sensitive skin or a history of allergies, consider consulting a dermatologist before use.

In summary, while it is possible to use hair dye like Garnier Black Naturals on a moustache, it should be done with caution, proper testing, and awareness of potential skin reactions. If unsure, seeking professional advice is recommended.