Examine source code of Dark Theme - Overlord

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Dark Skull",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right center"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0.41)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgba(0, 0, 0, 0.13)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 76, 0)",
      "popup": "rgba(0, 0, 0, 0.92)",
      "popup_text": "rgb(255, 255, 255)",
      "icons": "rgb(193, 58, 0)",
      "ntp_background": "rgb(0, 0, 0)",
      "popup_border": "rgb(255, 76, 0)",
      "tab_selected": "rgb(15, 4, 0)",
      "toolbar_top_separator": "rgba(255, 76, 0, 0.53)",
      "tab_loading": "rgb(255, 76, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{880a813d-72d7-485c-ba7b-bfb1487bf17f}"
    }
  }
}