Yes, and it was only shown in humans in 2021. Researchers scanned single hairs along their length and found pigment switching off in the exact weeks a person was under strain — the hair itself carries a record.
Transcript
Stress turns hair gray. That one is true, and it was only proven in humans in 2021. Researchers scanned single hairs along their length and found the pigment switching off in the exact weeks a person was under strain. Then the surprising part. When the stress lifted, a few of those hairs turned dark again. One volunteer went on holiday. Five hairs on their head reversed.
The surprising part came next: when the stress lifted, some of those hairs darkened again further up the shaft. One volunteer went on holiday and five hairs changed back. Grey from ageing is a different story, and that one does not come back.