This code simply demonstrates how to ask the user for a colour, and then enumerate all the button controls within a panel setting their background colour.

'place a panel on your form called pnlObjects
'in that panel place some buttons
'add a button to you form and call it cmdChangeColour
Private Sub cmdChangeColour_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdChangeColour.Click
        Try
            Dim cDlg As New ColorDialog
            Dim selColour As Color = Color.White
            'get the user colour
            With cDlg
                .ShowDialog()
                .AnyColor = True
                selColour = .Color
            End With
            'set all the controls in the panel to that colour
            For Each c As Control In pnlObjects.Controls
                If TypeOf c Is Button Then
                    Dim b As Button = CType(c, Button)
                    With b
                        .BackColor = selColour
                    End With
                End If
            Next
        Catch ex As Exception
            Throw New Exception(ex.Message)
        End Try
    End Sub
End Class