Examine source code of dark two grey color

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "dark two color grey",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(71, 78, 89, 0.48)",
      "toolbar_text": "rgba(206, 230, 255, 0.78)",
      "frame": "rgb(12, 19, 30)",
      "tab_background_text": "rgb(127, 143, 162)",
      "toolbar_field": "rgb(76, 77, 93)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(43, 138, 241, 0.78)",
      "popup": "rgb(76, 77, 93)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgba(43, 138, 241, 0.78)"
    }
  }
}