FieldAssistColors defines protocol for retrieving colors that can be used to
provide visual cues with fields. For consistency with JFace dialogs and
wizards, it is recommended that FieldAssistColors is used when colors are
used to annotate fields.
Color resources that are returned using methods in this class are maintained
in the JFace color registries, or by SWT. Users of any color resources
provided by this class are not responsible for the lifecycle of the color.
Colors provided by this class should never be disposed by clients. In some
cases, clients are provided information, such as RGB values, in order to
create their own color resources. In these cases, the client should manage
the lifecycle of any created resource.