Examine source code of Black visible Theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "theme test",
  "theme": {
    "colors": {
      "frame": [
        47,
        95,
        166
      ],
      "tab_background_text": [
        255,
        255,
        255
      ],
      "ntp_background": [
        75,
        75,
        75
      ],
      "ntp_text": [
        51,
        51,
        51
      ],
      "tab_selected": [
        255,
        255,
        225
      ],
      "tab_text": [
        0,
        0,
        0
      ],
      "toolbar": [
        0,
        0,
        0
      ],
      "tab_background_separator": "red"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f839e052-1ba8-47ae-95fc-f08a34c09f4e}"
    }
  }
}