private void add(Set<Color> colors, HighlightToken hlToken) {
		if (hlToken != null) {
			colors.add(hlToken.getColor());
		}
	}
Adds the given secondary highlighter, but does not create any highlights.  All secondary
highlighters pertain to a given function.
@param function the function
@param highlighter the highlighter
Ghidra/Features/Decompiler/src/main/java/ghidra/app/decompiler/component/ClangHighlightController.java