Examine source code of Darker Grey

{
  "name": "Almost Black",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "black-grey-gradient-linear-1920x1080-c2-000000-808080-a-135-f-14.jpg"
    },
    "colors": {
      "frame": "rgba(38, 38, 38, 1)",
      "tab_background_text": "rgba(222, 222, 222, 1)",
      "toolbar": "rgba(87, 87, 87, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(87, 87, 87, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(0, 0, 0, 0)"
    }
  }
}