Examine source code of NEPU

{
  "manifest_version": 2,
  "version": "1.15",
  "name": "NEPU",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png",
        "images/1.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right center",
        "left top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat",
        "repeat"
      ]
    },
    "colors": {
      "tab_line": "rgb(232, 181, 254)",
      "tab_background_text": "rgb(232, 181, 254)",
      "frame": "rgb(16, 4, 35)",
      "tab_loading": "rgb(232, 181, 254)", // Firefox 60
      "icons_attention": "rgb(232, 181, 254)", // Firefox 60

      "toolbar": "rgba(27, 8, 54, 0.8)",
      "bookmark_text": "rgb(153, 218, 252)",
	  "toolbar_bottom_separator": "rgba(27, 8, 54, 0.8)",
      "toolbar_vertical_separator": "rgba(232, 181, 254, 0.5)",

      "toolbar_field": "rgba(99, 86, 135, 0.65)",
      "toolbar_field_text": "rgb(232, 181, 254)",
      "toolbar_field_separator": "rgba(232, 181, 254, 0.5)", // Firefox 59
	  "toolbar_field_border_focus": "rgba(63, 43, 94, 0.97)",

      "button_background_hover": "rgba(99, 86, 135, 0.65)", // Firefox 60
      "button_background_active": "rgba(77, 55, 135, 0.65)", // Firefox 60

      "popup": "rgba(27, 8, 54, 0.85)", // Firefox 60
      "popup_text": "rgb(232, 181, 254)", // Firefox 60
	  "popup_highlight": "rgb(232, 181, 254)",
	  "popup_highlight_text": "black",
      "popup_border": "rgba(63, 43, 94, 0.97)",

      "ntp_text": "white", // Firefox 63
      "ntp_background": "rgb(16, 4, 35)", // Firefox 63

      "sidebar": "rgb(16, 4, 35)", // Firefox 63
      "sidebar_text": "rgb(232, 181, 254)", // Firefox 63
      "sidebar_border": "rgba(63, 43, 94, 0.97)", // Firefox 64
      "sidebar_highlight": "rgba(99, 86, 135, 0.65)" // Firefox 63
    }
  }
}