Examine source code of kanagawa_theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "kanagawa",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(31, 31, 40)",
      "toolbar_text": "rgb(200, 192, 147)",
      "frame": "rgb(31, 31, 40)",
      "tab_background_text": "rgb(84, 84, 109)",
      "toolbar_field": "rgb(22, 22, 29)",
      "toolbar_field_text": "rgb(200, 192, 147)",
      "tab_line": "rgb(200, 192, 147)",
      "popup": "rgb(31, 31, 40)",
      "popup_text": "rgb(200, 192, 147)",
      "button_background_active": "rgb(34, 50, 73)",
      "button_background_hover": "rgb(34, 50, 73)",
      "popup_highlight_text": "rgb(220, 215, 186)",
      "popup_highlight": "rgb(34, 50, 73)",
      "tab_loading": "rgb(34, 50, 73)",
      "toolbar_field_border_focus": "rgb(31, 31, 40)",
      "toolbar_field_border": "rgb(31, 31, 40)",
      "toolbar_field_highlight": "rgb(34, 50, 73)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{53cc1853-5ebd-41c8-8c89-6524cb99b99e}"
    }
  }
}