Examine source code of Light Grey Theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Edge-dark-like",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(76, 76, 76)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(51, 51, 51)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(36, 36, 36)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(76, 76, 76)",
      "popup": "rgb(36, 36, 36)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(76, 76, 76)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{fd351ab2-a264-4674-8a22-7f49c1f6c59b}"
    }
  }
}