It looks fine for Herring Gull. I see no sign of brown, very little dark on the bill, and the white wing spots look clean and well formed so I assume it's an adult.
Brown feathers in the mantle and wing coverts of large, white-headed gulls are generally an indication of immaturity. If you go to the Herring Gull account on BirdFellow (link below) and look at ID photo #16, you can see blackish-brown coloration on the wing coverts while the black in the primary feathers looks more like an adult. This bird is probably about one year shy of being a full adult.
Gull ID?
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