Examine source code of matte black (for proton)

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "mate black (for proton)",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(34, 34, 34)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(229, 229, 229)",
      "toolbar_field": "rgb(0, 0, 0)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(205, 35, 185, 0)",
      "popup": "rgb(31, 34, 61)",
      "popup_text": "rgb(215, 226, 239)",
      "tab_selected": "rgba(208, 156, 217, 0)",
      "tab_text": "rgb(208, 156, 217)",
      "toolbar_field_highlight": "rgba(193, 50, 50, 0.83)",
      "toolbar_field_separator": "rgba(232, 232, 232, 0)",
      "toolbar_top_separator": "rgba(232, 232, 232, 0)",
      "tab_loading": "rgba(205, 35, 185, 0)"
    }
  }
}