Thanks Vinz. You rule. For anybody who's interested, here's the full code I used to color just one cell of a row with RowDataBound, which allows the rest of the row to be highlighted in another color by using the SelectedRowStyle-BackColor in the aspx page:
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
//ensure that the row is a data row (not a header or footer)
if (e.Row.RowType == DataControlRowType.DataRow)
{
//retrieve the dataitem, and cast it to the appropriate type
DataRowView drv = e.Row.DataItem as DataRowView;
//determine the value of the Status field
if (drv["column0"].ToString().Equals("Blah"))
{
e.Row.Cells[3].BackColor = System.Drawing.Color.Red;
}
}
}