Examine source code of First theme

{
  "name": "First theme",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "1ab089aaf438547bc56b14d3e597807d.jpg"
    },
    "colors": {
      "frame": "rgba(0, 28, 94, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{015ad8b0-637d-4814-9f94-f8170fefcbea}"
    }
  }
}