Examine source code of Earthly Theme

{
  "name": "Blue and Green",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "1x1-00000000.png"
    },
    "colors": {
      "frame": "rgba(34, 116, 165, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(50, 147, 111, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(42, 122, 92, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(50, 147, 111, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d85eea92-5618-4eb3-8990-ddcd2b7e3b2b}"
    }
  }
}