private boolean isExternalLink(HyperlinkEvent e) {
		String description = e.getDescription();
		return description != null && EXTERNAL_URL_PATTERN.matcher(description).matches();
	}
A mapping of known style sheet colors to convert from the values in the style sheet to colors
defined in the system theme.
Ghidra/Framework/Help/src/main/java/help/GHelpHTMLEditorKit.java