Examine source code of LightGrey for Thunderbird

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "LightGrey Design for Thunderbird",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(43, 43, 33, 0)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(83, 83, 83)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(225, 229, 232)",
      "toolbar_field_text": "rgb(0, 0, 0)",
      "tab_line": "rgba(0, 0, 0, 0.94)",
      "popup": "rgb(255, 255, 255)",
      "popup_text": "rgb(0, 0, 0)",
      "button_background_active": "rgb(160, 0, 255)",
      "button_background_hover": "rgb(255, 90, 0)",
      "ntp_background": "rgb(200, 200, 200)",
      "ntp_text": "rgba(50, 50, 50, 0)",
      "tab_loading": "rgb(0, 0, 0)",
      "tab_selected": "rgb(255, 90, 0)",
      "tab_text": "rgb(255, 255, 255)",
      "toolbar_field_border_focus": "rgb(255, 90, 0)",
      "toolbar_field_highlight": "rgb(160, 0, 255)",
      "toolbar_top_separator": "rgba(147, 135, 174, 0)"
    }
  }
}