Examine source code of Winter January

{
  "name": "Winter January",
  "manifest_version": 2,
  "version": "4.0",
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "rgba(255, 255, 255, 1)",
      "tab_background_text": "rgba(0, 0, 0, 1)",
      "toolbar": "rgba(255, 245, 245, 0)",
      "bookmark_text": "rgba(0, 0, 0, 1)",
      "toolbar_field": "rgba(255, 255, 255, 0.1)",
      "toolbar_field_text": "rgba(0, 0, 0, 1)",
      "tab_line": "rgba(10, 10, 10, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{565f9fb8-79bd-47b0-ac16-1b85bdb39de4}"
    }
  }
}