Examine source code of Grace Bros.

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Grace Bros.",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(22, 72, 75, 0)",
      "toolbar_text": "rgb(243, 248, 248)",
      "frame": "rgb(22, 54, 75)",
      "tab_background_text": "rgb(0, 1, 4)",
      "toolbar_field": "rgba(0, 0, 0, 0)",
      "toolbar_field_text": "rgba(245, 245, 245, 0)",
      "tab_line": "rgb(251, 251, 251)",
      "popup": "rgb(22, 54, 75)",
      "popup_text": "rgb(251, 131, 165)",
      "tab_loading": "rgb(251, 251, 251)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0a65a5f1-db5f-438e-a5a1-7df07ff8afc0}"
    }
  }
}