Examine source code of Kasane Teto dark mode

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Kasane Teto Dark Theme",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right bottom"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(55, 55, 55)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(36, 36, 36)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(36, 36, 36)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(151, 28, 28)",
      "popup": "rgb(55, 55, 55)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(140, 140, 140)",
      "popup_border": "rgb(151, 28, 28)",
      "tab_selected": "rgb(151, 28, 28)",
      "tab_loading": "rgb(151, 28, 28)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{411b1ff6-c3e1-42a4-95e3-098f4dc830c4}"
    }
  }
}