Examine source code of Adwaita-Dark

{
  "manifest_version": 2,
  "version": "1.3",
  "name": "Adwaita-Dark",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(57, 63, 63)",
      "toolbar_text": "rgb(201, 204, 204)",
      "frame": "rgb(41, 41, 41)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(45, 51, 53)",
      "toolbar_field_text": "rgb(230, 241, 241)",
      "tab_line": "rgb(41, 41, 41)",
      "popup": "rgb(45, 51, 53)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(45, 51, 53)",
      "popup_border": "rgb(34, 69, 104)",
      "sidebar_border": "rgb(34, 69, 104)",
      "toolbar_field_border_focus": "rgb(34, 69, 104)",
      "toolbar_field_border": "rgb(34, 69, 104)",
      "toolbar_top_separator": "rgb(45, 51, 53)",
      "tab_loading": "rgb(41, 41, 41)"
    }
  }
}