public void setOutline( Object outline ) {
		putClientProperty( OUTLINE, outline );
	}
Specifies the outline color of the component border.
<p>
Allowed Values are:
<ul>
    <li>{@code null}
    <li>string {@code "error"}
    <li>string {@code "warning"}
    <li>any color (type {@link Color})
    <li>an array of two colors (type {@link Color}[2]) where the first color
        is for focused state and the second for unfocused state
</ul>
flatlaf-extras/src/main/java/com/formdev/flatlaf/extras/components/FlatPasswordField.java