Examine source code of skull_blue

{
  "name": "skull_blue",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "skull_firefox_blue1.png"
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0.1)",
      "toolbar_field": "rgba(0, 0, 0, 0.1)",
      "toolbar_field_text": "rgba(63, 121, 245, 1)",
      "frame": "rgba(0, 0, 0, 1)",
      "tab_background_text": "rgba(153, 168, 255, 1)",
      "bookmark_text": "rgba(91, 114, 240, 1)"
    }
  }
}