private void changeColor_Tool (object sender, EventArgs e)
    {

            ForeColor = Color.Coral;
    }

for(int i=0;i<10;i++)
        {
            var changeColor = new CheckBox();
            changeColor.CheckedChanged += ChangeColor_CheckedChanged;
          //Добавление на контрол или в коллекцию
        }
bool havecheck = false;
private void ChangeColor_CheckedChanged(object sender, EventArgs e)
    {
        var havecheck = !havecheck;//Cделал тернарным опертором
        var checkbox = (CheckBox)sender;
        checkbox.ForeColor = havecheck ? Color.Coral : Color.Black;
    }

public Form1()
{
    InitializeComponent();
    foreach (CheckBox checkBox in this.Controls)
    {
       checkBox.CheckStateChanged += CheckBoxOnCheckStateChanged;
    }
}

private void CheckBoxOnCheckStateChanged(object sender, EventArgs eventArgs)
{
    var senderBox = (CheckBox) sender;
    senderBox.ForeColor = senderBox.Checked ? Color.Coral : Color.Black;
}