Examine source code of Theme for Nightly 2

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Theme for Nightly 2",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(25, 11, 33, 0.85)",
      "toolbar_text": "rgb(0, 178, 178)",
      "frame": "rgb(22, 75, 106)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgba(25, 11, 33, 0)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(0, 178, 178)",
      "popup": "rgb(25, 11, 33)",
      "popup_text": "rgb(0, 178, 178)",
      "tab_loading": "rgb(0, 178, 178)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ab74fafe-ef7c-45e1-8789-be6dd204b062}"
    }
  }
}