namespace DataGridViewOperation
{
    public partial class Form1 : Form
    {     
        SqlConnection sqlcon = new SqlConnection(@"Server=RAVI-PC\SQLEXPRESS;database=test1;uid=ravindran;pwd=srirangam;");
        SqlCommand sqlcmd = new SqlCommand();
        SqlDataAdapter da = new SqlDataAdapter();
        DataTable dt = new DataTable();
        
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            LoadGrid();
            //Change back color using below method after bind data
            colorchange();
        }

        void LoadGrid()
        {
            sqlcon.Open();
            sqlcmd = new SqlCommand("select * from emp", sqlcon);
            da = new SqlDataAdapter(sqlcmd);
            da.Fill(dt);
            bind = true;
            dataGridView1.DataSource = dt;
            sqlcon.Close();           
        }
        void colorchange()
        {            
            for(int i =0;i<=99;i++)
            {
                dataGridView1.Rows[i].DefaultCellStyle.BackColor = Color.Aqua;
            }
            for(int i =100;i<=199;i++)
            {
                dataGridView1.Rows[i].DefaultCellStyle.BackColor = Color.Blue;
            }
            //Make sure split rows based on row count if row is not in that count may be index out of range exception come.
        }
}
}