The phrase "a gentle appearance" is correct and usable in written English.
It can be used to describe someone or something that has a soft, mild, or soothing look or demeanor.
Example: "The painting had a gentle appearance, with soft colors and delicate brush strokes that evoked a sense of calm."
Alternatives: "a soft look" or "a mild demeanor."
Their parents were from Barbados: Aubrey, tall, handsome, and stiff, and Gloria, whose soft eyes gave her a gentle, yielding appearance.
But his gentle appearance and his experience of the British way of life haven't stopped him becoming a tyrannical monster.
The New Zealand Kennel Club warns against keeping them with dogs that have dominant personalities, "as once challenged they are terrifying fighters, despite their gentle appearance", but otherwise the breed is good with other dogs.
The "lions of Buddha" (often miscalled dogs) are frequently represented, as is the qilin, which is a composite animal, not unlike a unicorn, that has a fierce appearance but a gentle disposition.
The gray-haired Cornell-trained psychiatrist has a gentle, serious manner, and his appearance, together with the generic shrink décor of his office — leather couch, granite-topped coffee table — makes this pronouncement seem particularly jarring.
Press accounts were usually positive, pointing out that, for all of his gruff outward appearance, he was a gentle soul.
There's a gentle message about judging people by appearances and being a prisoner of good looks and vanity.
Daniel wanted a softer appearance, and asked for something rounded, perhaps with a gentle curve.
Mice were evaluated for general health, including body weight and length, appearance of fur and whiskers, reflexive reactions to a gentle touch from a cotton swab to the whiskers and the visual placing reflex.
A gentle, genial, good-humoured, humorous man, as generous in spirit as in appearance, his consistently entertaining flood of talk reflected his vast enthusiasms.
