You probably want to use the RowDataBound event of the GridView, something like this:
<asp:GridView ID="grid1" runat="server" AutoGenerateColumns="False"
DataSourceID="SqlDataSource3" OnRowDataBound="ChangeRowColor">
protected void ChangeRowColor(object sender, GridViewRowEventArgs e)
{
if( ((DataRow)e.Row.DataItem)[1] == .5)
{
e.Row.Cell[1].BackColor = Colors.Green;
}
}
In my example, I'm assuming the data used to fill the grid are DataRows (i.e. from a datatable), but essentially the idea is to cast the DataItem of the current row to whatever type of object is being bound to, check the value of the property you need, and then set the BackColor of the corresponding cell.
You could also inspect the Cell's text property, but you might have to do extra parsing or what-not to get from the string to whatever value you want to compare.