Examine source code of gradient red black

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Red gradient",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(24, 63, 80, 0.2)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(228, 228, 228)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(228, 228, 228)",
      "toolbar_field_text": "rgb(0, 0, 0)",
      "tab_line": "rgb(0, 0, 0)",
      "popup": "rgba(219, 88, 100, 0.95)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_hover": "rgba(219, 88, 100, 0.95)",
      "icons": "rgb(228, 228, 228)",
      "ntp_background": "rgb(68, 62, 63)",
      "ntp_text": "rgb(255, 255, 255)",
      "popup_border": "rgba(255, 255, 255, 0.5)",
      "sidebar_border": "rgb(83, 83, 83)",
      "sidebar_highlight_text": "rgba(219, 88, 100, 0.95)",
      "tab_background_separator": "rgb(162, 186, 223)",
      "tab_selected": "rgba(10, 164, 137, 0)",
      "tab_text": "rgb(255, 255, 255)",
      "toolbar_field_border_focus": "rgb(228, 228, 228)",
      "toolbar_field_highlight": "rgba(219, 88, 100, 0.95)",
      "tab_loading": "rgb(0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d4f6bfe4-439f-4978-8046-42427bb3e874}"
    }
  }
}