Examine source code of BlueGradientTheme

{
  "name": "BlueTheme",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "340452.png"
    },
    "colors": {
      "frame": "rgba(49, 79, 148, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{83bef8af-87f6-4db6-a4bf-7859f11757b8}"
    }
  }
}