Examine source code of rain_reminder

{
  "name": "rain_reminder",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "tropical_rain.jpg"
    },
    "colors": {
      "frame": "rgba(169, 217, 180, 0.88)",
      "tab_background_text": "rgba(103, 120, 111, 1)",
      "toolbar": "rgba(100, 138, 113, 0.71)",
      "bookmark_text": "rgba(23, 97, 60, 1)",
      "toolbar_field": "rgba(192, 219, 212, 0.81)",
      "toolbar_field_text": "rgba(55, 107, 94, 1)",
      "tab_line": "rgba(217, 217, 217, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d0586ac0-a8a9-4064-9f45-b98a6af9c9b0}"
    }
  }
}