What could cause gray patches on the skin above the eyebrows and upper lip?

Melasma: Melasma is caused by hormones in women usually associated with pregnancy, oral contraceptives, hormonal replacement therapy, etc. It can appear brown, gray, or brown-black. Other causes of gray discoloration are sun damage, post-inflammatory hyperpigmentation, reaction to medications (ie: minocycline).

Eczema or dry skin: Eczema or dry skin can cause this issue. Try washing your face regularly and using skin lotion/moisturizer. If no improvement, see a dermatologist.