Public Class Form1
    Private farbe As Integer = 0
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Select Case Me.Button1.Tag
            Case 0
                Me.Button1.Tag = 1
                Me.Button1.Text = "Beenden"
                Me.Timer1.Enabled = True
            Case 1
                Me.Button1.Tag = 0
                Me.Button1.Text = "Start"
                Me.Timer1.Enabled = False
        End Select
 
    End Sub
 
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        If farbe = 4 Then
            farbe = 0
        End If
        Select Case farbe
            Case 0
                Panel1.BackColor = Color.Blue
            Case 1
                Panel1.BackColor = Color.Green
            Case 2
                Panel1.BackColor = Color.Red
            Case 3
                Panel1.BackColor = Color.Yellow
        End Select
        farbe += 1
    End Sub
End Class