Examine source code of Light Theme for Firefox

{
  "manifest_version": 2,
  "homepage_url": "https://www.turnoffthelights.com",
  "theme": {
    "colors": {
      "frame": "white",
      "tab_background_text": "#000",
      "toolbar": "white",
      "toolbar_field": "white",
      "toolbar_field_text": "black",
      "toolbar_field_border": "#ccc",
      "tab_line": "black",
      "popup": "white",
      "popup_text": "black",
      "popup_border": "#ccc",
      "ntp_background": "white",
      "ntp_text": "black"
    }
  },
  "name": "Light theme for Firefox",
  "version": "1.0.2.1resigned1",
  "description": "A light Firefox theme for your web browser. It's simple and coherent.",
  "author": "Stefan vd",
  "applications": {
    "gecko": {
      "id": "{362e566c-9de2-401f-9fa7-6853f4b69d99}",
      "strict_min_version": "63.0"
    }
  }
}