public class GridColoredColumn : DataGridTextBoxColumn
{
	protected override void Paint(System.Drawing.Graphics g, System.Drawing.Rectangle bounds,
		System.Windows.Forms.CurrencyManager source, int rowNum, System.Drawing.Brush backBrush, 
		System.Drawing.Brush foreBrush, bool alignToRight)
	{
		object obj = this.GetColumnValueAtRow(source, rowNum);
		 //в зависимости от obj определяешь backBrush и foreBrush 
		base.Paint(g, bounds, source, rowNum, backBrush, foreBrush, alignToRight);
	}
}