+`OPT_COLOR_FLAG(short, long, &int_var, description)`::
+ Introduce an option that takes an optional argument that can
+ have one of three values: "always", "never", or "auto". If the
+ argument is not given, it defaults to "always". The `--no-` form
+ works like `--long=never`; it cannot take an argument. If
+ "always", set `int_var` to 1; if "never", set `int_var` to 0; if
+ "auto", set `int_var` to 1 if stdout is a tty or a pager,
+ 0 otherwise.
+