Setting a ReadOnly TextBox default BackColor

I have a TextBox which is set to be ReadOnly.
At some point that TextBox is being available for editing, and it's BackColor changes (It is indicating if the value is valid).
If I want to set the TexBox back to ReadOnly, the TextBox doesn't get back the original BackColor that a ReadOnly TextBox gets.
What should I do in order to get the original color again?
I realize I can set the color manually to SystemColors.Control, but is this the "right way"?

Code Sample

This is a simple code for demonstration. If SystemColors.Control is the way to go, I will change it in the ReadOnlyChanged event...

private void button1_Click(object sender, EventArgs e)
{
    //At this point this.textBox1 is ReadOnly
    this.textBox1.ReadOnly = false;
    this.textBox1.BackColor = Color.Orange;


    /*this.textBox1.BackColor = SystemColors.Control;*/ //Is this the right way?
    this.textBox1.ReadOnly = true; //Textbox remains orange...
}