How to: Change the Appearance of the Windows Forms ColorDialog Component
You can configure the appearance of the Windows Forms ColorDialog component with a number of its properties. The dialog box has two sections — one that shows basic colors and one that allows the user to define custom colors.
Most of the properties restrict what colors the user can select from the dialog box. If the AllowFullOpen property is set to true, the user is allowed to define custom colors. The FullOpen property is true if the dialog box is expanded to define custom colors; otherwise the user must click a "Define Custom Colors" button. When the AnyColor property is set to true, the dialog box displays all available colors in the set of basic colors. If the SolidColorOnly property is set to true, the user cannot select dithered colors; only solid colors are available to select.