Examine source code of DarkThemeByHF

{
  "manifest_version": 2,
  "version": "1.1",
  "name": "Darker",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(76, 79, 90)",
      "toolbar_text": "rgb(233, 233, 233)",
      "frame": "rgb(42, 44, 51)",
      "tab_background_text": "rgb(169, 153, 156)",
      "toolbar_field": "rgb(63, 64, 71)",
      "toolbar_field_text": "rgb(204, 204, 207)",
      "tab_line": "rgb(108, 155, 108)",
      "popup": "rgb(48, 39, 55)",
      "popup_text": "rgb(225, 217, 225)",
      "ntp_background": "rgb(28, 28, 36)",
      "ntp_text": "rgb(138, 138, 138)",
      "popup_border": "rgb(24, 20, 28)",
      "tab_loading": "rgb(108, 155, 108)"
    }
  }
}