Examine source code of Tema

{
  "name": "SV",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "stardew valley2.jpg"
    },
    "colors": {
      "frame": "rgba(59, 76, 115, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(89, 133, 92, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(122, 117, 117, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(46, 255, 192, 0.42)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8b15d318-0f97-4514-9c36-a2741f8b2316}"
    }
  }
}