Does Providential Instinct — if a creature has hexproof, can its controller still target it with their own auras?

Hexproof is a keyword ability defined in CR 702.11b: a permanent with hexproof can't be the target of spells or abilities your opponents control. The key word is 'opponents' — the ability places no restriction on what the creature's own controller can do.

So when you want to attach your own Aura to your hexproof creature, you cast the Aura spell and target your creature as normal (CR 303.4, which governs Aura targeting on the stack). Because hexproof only shields the creature from opponents' targeting, your own targeting is completely unaffected.

This is a common point of confusion because Shroud (CR 702.18b) — hexproof's older cousin — prevents all players, including the controller, from targeting the permanent. Hexproof was designed specifically to allow the friendly interaction while blocking hostile ones.

Concrete example: You control a Slippery Bogle (a creature with hexproof). Your opponent cannot cast Pacifism on it. However, you can freely cast Ethereal Armor and target Slippery Bogle with it, attaching the Aura to it without any issue.

References: CR 702.11b (hexproof definition), CR 702.18b (shroud for contrast), CR 303.4 (Aura spell targeting rules).