Visual Basic (Problem)

[Ich5003]

Hallo Leute, ich habe folgenden Code:

        Dim choose_(points) As Integer
        Dim round As Integer = 0
        choose_(points) = random.Next(1, 5)
        Do
            MsgBox(choose_(points))
            If choose_(round) = 1 Then btn_green.BackColor = Color.White
            If choose_(round) = 2 Then btn_red.BackColor = Color.White
            If choose_(round) = 3 Then btn_yellow.BackColor = Color.White
            If choose_(round) = 4 Then btn_blue.BackColor = Color.White
            threading.thread.sleep(2000)
            btn_green.BackColor = Color.Green
            btn_red.BackColor = Color.Red
            btn_yellow.BackColor = Color.Yellow
            btn_blue.BackColor = Color.Blue
            round += 1
        Loop Until round > points

Nur leider ändert sich die Farbe meiner Button nicht, was soll ich tun?