Color Rows In DataGridView
SqlConnection, SqlCommand and SqlDataAdapter are implementing the IDisposable interface. Enclosing the usage of these objects inside a using statement ensures that the objects will always be proper disposed because the using statement just equals a try...finally where the objects would be disposed in the finally part.  

The main problem regarding your performance issue is, that by calling the AutoResizeColumns() method the event will be triggered for each row and each column.
This results for each row and each column that you iterate over every row in the DataGridView.

So if we assume you have 12,000 rows with at least 5 columns .... you can do the math yourself.

The DataGridViewCellFormattingEventArgs has a property RowIndex which allows to access a single row so you should use this.  

Summing this up in some code could look like so  

private bool shouldFormattingBeDone = false;
private void PopulateIT()
{
    datagridview1.Visible = true;
    lblNoData.Visible = false;

    string connString = @"Connection String";
    string query = @"SELECT * from tempdata";

    using (SqlConnection conn = new SqlConnection(connString))
    using (SqlCommand cmd = new SqlCommand(query, conn))
    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
    {
        conn.Open();
        da.Fill(formattedDT);
    }
    datagridview1.DataSource = formattedDT;

    shouldFormattingBeDone = false;
    datagridview1.AutoResizeColumns();
    shouldFormattingBeDone = true;
}


private void datagridview1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
    if (shouldFormattingBeDone == false) { return; }

    DataGridViewRow row = datagridview1.Rows[e.RowIndex];

    if (row.Cells["Jake"].Value == System.DBNull.Value &amp;&amp; row.Cells["Jones"].Value == System.DBNull.Value &amp;&amp; row.Cells["Lati"].Value == System.DBNull.Value &amp;&amp; row.Cells["Venitia"].Value == System.DBNull.Value)
    {
        row.DefaultCellStyle.BackColor = Color.Red;
    }

}


This could be beautified by having an extension method which takes a DataGridViewCell as a parameter like so  

public static class DataGridViewExtension
{
    public static bool IsDbNull(this DataGridViewCell cell)
    {
        return cell.Value == DBNull.Value;
    }
}  


resulting in  the if condition looking like so  

if (row.Cells["Jake"].IsDbNull() &amp;&amp; row.Cells["Jones"].IsDbNull() &amp;&amp; row.Cells["Lati"].IsDbNull() &amp;&amp; row.Cells["Venitia"].IsDbNull())  


PS: I can't remember if the connection needs to be open when the constructor of the SqlDataAdapter is called.