Here is an example of code that changes the assigned style of a cell and update this cell immediately:
private void button1_Click(object sender, EventArgs e)
{
iGrid1.Cells[2, 1].Style.BackColor = Color.Aqua;
iGrid1.Invalidate(iGrid1.Cells[2, 1].GetBounds(true));
iGrid1.Update();
}
If several cells share the same style and you change a property of that style object, call the Invalidate method without parameters.