Per the Cornell website: "Orange-crowned Warblers aren’t the most dazzling birds in their family, but they’re a useful one to learn. These grayish to olive-green birds vary in color geographically and have few bold markings. There’s rarely any sign of an orange crown, which is usually only visible when the bird is excited and raises its head feathers. They might have you scratching your head until you recognize their slim shape, sharply pointed bill, and warmer yellow under the tail. These busy birds forage low in shrubs, and are one of the few warblers that's more common in the West "
Here are some pics from Sunset Beach, NC. I like them because usually you can't make out the orange crown, but here you just barely can see it.