Examine source code of blue signs

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "blue signs",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(233, 237, 240)",
      "toolbar_text": "rgb(64, 64, 90)",
      "frame": "rgb(36, 117, 164)",
      "tab_background_text": "rgb(248, 248, 248)",
      "toolbar_field": "rgb(252, 252, 252)",
      "toolbar_field_text": "rgb(10, 10, 10)",
      "tab_line": "rgba(251, 37, 77, 0.96)",
      "popup": "rgb(233, 237, 240)",
      "popup_text": "rgb(11, 11, 11)",
      "tab_loading": "rgba(251, 37, 77, 0.96)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2a7010cb-6dd7-4eb2-97eb-a8e2429cdb0f}"
    }
  }
}