How to detect button color and change?

I try to detect button color and change it to another color but I couldn't do. My codes are given below. If the button color is red and pressed on it, button color should change to green. If the button color is green and pressed on it, button color should change to red. What is my fault here?

Code:

  ub BtnSystemOnOff_Click
If TextFieldimei.Text.Length = 15 Then
    BtnSystemOnOff.Tag = BtnSystemOnOff.Background
If (BtnSystemOnOff.Tag = Colors.Red) Then
    BtnSystemOnOff.Color =...  

How to detect button color and change?

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