[c#] Changing datagridview cell color dynamically

I have a dataGridView object that is populated with data. I want to click a button and have it change the color of the background of the cell. This is what I currently have

foreach(DataGridViewRow row in dataGridView1.Rows)
{
    foreach(DataGridViewColumn col in dataGridView1.Columns)
    {
            //row.Cells[col.Index].Style.BackColor = Color.Green; //doesn't work
            //col.Cells[row.Index].Style.BackColor = Color.Green; //doesn't work
        dataGridView1[col.Index, row.Index].Style.BackColor = Color.Green; //doesn't work
    }
} 

ALL of these three cause the table to be redrawn over itself in an overlapping manner and trying to re-size the tables becomes a mess. when clicking on a cell, the value remains highlighted and the backcolor doesn't change.

Q: How can I change the backcolor of an individual cell after the table exists?

If you want every cell in the grid to have the same background color, you can just do this:

dataGridView1.DefaultCellStyle.BackColor = Color.Green;

Implement your own extension of DataGridViewTextBoxCell and override Paint method like this:

class MyDataGridViewTextBoxCell : DataGridViewTextBoxCell
{
    protected override void Paint(Graphics graphics, Rectangle clipBounds, Rectangle cellBounds, int rowIndex,
        DataGridViewElementStates cellState, object value, object formattedValue, string errorText,
        DataGridViewCellStyle cellStyle, DataGridViewAdvancedBorderStyle advancedBorderStyle, DataGridViewPaintParts paintParts)
    {
        if (value != null)
        {
            if ((bool) value)
            {
                cellStyle.BackColor = Color.LightGreen;
            }
            else
            {
                cellStyle.BackColor = Color.OrangeRed;
            }
        }
        base.Paint(graphics, clipBounds, cellBounds, rowIndex, cellState, value,
            formattedValue, errorText, cellStyle, advancedBorderStyle, paintParts);
}

}

Then in the code set CellTemplate property of your column to instance of your class

columns.Add(new DataGridViewTextBoxColumn() {CellTemplate = new MyDataGridViewTextBoxCell()});

Considere use DataBindingComplete event for update the style. The next code change the style of the cell:

    private void Grid_DataBindingComplete(object sender, DataGridViewBindingCompleteEventArgs e)
    {
        this.Grid.Rows[2].Cells[1].Style.BackColor = Color.Green;
    }

Thanks it working

here i am done with this by qty field is zero means it shown that cells are in red color

        int count = 0;

        foreach (DataGridViewRow row in ItemDg.Rows)
        {
            int qtyEntered = Convert.ToInt16(row.Cells[1].Value);
            if (qtyEntered <= 0)
            {
                ItemDg[0, count].Style.BackColor = Color.Red;//to color the row
                ItemDg[1, count].Style.BackColor = Color.Red;

                ItemDg[0, count].ReadOnly = true;//qty should not be enter for 0 inventory                       
            }
            ItemDg[0, count].Value = "0";//assign a default value to quantity enter
            count++;
        }

    }