The Color Produced by a Color Dialog Box

At run time, you can set the color programmatically by assigning it a valid known name of a color:

Public Sub InitializeComponent()
            Dim dlgColor As ColorDialog = New ColorDialog()
            dlgColor.Color = Color.Red
            dlgColor.ShowDialog()
End Sub

When the user has finished using the Color dialog box and clicks OK, you can find out what color was selected by retrieving the value of the ColorDialog.Color property. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Private pnlColored As Panel
        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            Dim dlgColor As ColorDialog

            pnlColored = New Panel()
            pnlColored.Location = New Point(10, 10)
            pnlColored.Size = New Size(200, 150)
            Controls.Add(pnlColored)

            dlgColor = New ColorDialog()
            dlgColor.Color = Color.FromKnownColor(KnownColor.DarkTurquoise)

            If dlgColor.ShowDialog = Windows.Forms.DialogResult.OK Then
                pnlColored.BackColor = dlgColor.Color
            End If

        End Sub

    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

By default, the Color dialog box comes up in its regular (small) size. This allows the user to select one of the preset colors. If the desired color is not available, as mentioned already, the user can click the Define Custom Colors >> button. If you want to control the user's ability to expand the dialog box, use the Boolean AllowFullOpen property. When this property is set to True, which is its default value, the dialog box appears in its regular size but with the Define Custom Colors >> button enabled. If you want the user to be able to select only one of the preset colors and not have the ability to expand the dialog box, set the AllowFullOpen property to False. Here is an example:

Public Sub InitializeComponent()
            Dim dlgColor As ColorDialog

            dlgColor = New ColorDialog()

            dlgColor.AllowFullOpen = False

            dlgColor.ShowDialog()

End Sub

With this value, when the Color dialog box comes up, it is in its regular size but the Define Custom Colors >> button is disabled:

As mentioned already, by default, the Color dialog box displays in its regular size. You can control the regular or full size of the dialog using the Boolean FullOpen property. When its value is False, which is the default, the dialog appears regularly. If you want it to appear in its full size, set this property to True.