C# How to randomize a color on buttons in Form 2 from clicking a button on Form1

I am building a C# movie theater program. On Form1, when clicking on "Reserve" button I want the 21 buttons on Form 2 to randomly change 6 seats to "Red". I would like for it to be different seats every time the "Reserve" button is pressed on Form 1.

Here is the code I am trying to make work.

Random random = new Random();

private Color GetRandomColor()
{
    return Color.FromArgb(random.Next(0, 255), random.Next(0, 255), random.Next(0, 255));
}

private void reserve_button_Click(object sender, EventArgs e)
{
    button1.BackColor = GetRandomColor();
    button2.BackColor = GetRandomColor();
    button3.BackColor = GetRandomColor();
    button4.BackColor = GetRandomColor();
}

Movie Menu Picture Seating Selection