Examine source code of Red tab borders

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Red line",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-011-d53e0d0d1538ed554a90e056a2f04eca.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(248, 248, 248)",
      "toolbar_text": "rgb(41, 41, 41)",
      "frame": "rgb(233, 233, 233)",
      "tab_background_text": "rgb(104, 104, 104)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(41, 41, 41)",
      "tab_line": "rgb(229, 43, 43)",
      "popup": "rgb(255, 255, 255)",
      "popup_text": "rgb(41, 41, 41)",
      "sidebar": "rgb(219, 219, 219)",
      "tab_loading": "rgb(255, 255, 255)",
      "tab_selected": "rgb(255, 255, 255)",
      "tab_text": "rgb(41, 41, 41)"
    }
  }
}