Restricting colors for a custom control?

I have a custom class with a public property of type color as follows. When I
bind an instance of ManagementIndicator to PropertyGrid control it displays
the public Indicator property with color drop down box.

public class ManagementIndicator
{
private Color _indicator;

public Color Indicator
{
get { return _indicator; }
set { _indicator = value; }
}
}

Now I want to restrict the drop down to show only three color (Red, Orange
and Green). How can I do that? I don’t want it to show Custom, Web and System
tabs either. Is there anyway I can change the default behavior or is there
any color picker control available that I can use or do I have to create a
custom color drop down box?

Please help
Thanks