Examine source code of custom theme

{
  "name": "custom theme",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "unknown (1).png"
    },
    "colors": {
      "frame": "rgba(204, 132, 235, 1)",
      "tab_background_text": "rgba(140, 242, 159, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e1ab0f05-9ab5-433e-8335-60e1fab645e5}"
    }
  }
}