Examine source code of Tropical Fever...

{
  "name": "Tropical Fever...",
  "manifest_version": 2,
  "version": "5.0",
  "theme": {
    "images": {
      "theme_frame": "TropicalFeverH.jpg"
    },
    "colors": {
      "frame": "rgba(53, 79, 25, 1)",
      "tab_background_text": "rgba(224, 255, 226, 1)",
      "toolbar": "rgba(0, 0, 0, 0)",
      "bookmark_text": "rgba(237, 255, 235, 1)",
      "toolbar_field": "rgba(53, 79, 24, 0.07)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(255, 255, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{de6913bb-6635-4c84-9754-70caf8b3fac6}"
    }
  }
}