Examine source code of Tiny Bubbles...

{
  "name": "Tiny Bubbles...",
  "manifest_version": 2,
  "version": "6.0",
  "theme": {
    "images": {
      "theme_frame": "TinyBubblesHF.jpg"
    },
    "colors": {
      "frame": "rgba(51, 43, 22, 1)",
      "tab_background_text": "rgba(251, 255, 168, 1)",
      "toolbar": "rgba(0, 0, 0, 0)",
      "bookmark_text": "rgba(173, 251, 255, 1)",
      "toolbar_field": "rgba(51, 89, 102, 0.08)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(173, 251, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{db1a0310-e4ac-4646-9dd6-b28d98f678dc}"
    }
  }
}