<asp:TemplateField HeaderText="Importe" SortExpression="importe">
<EditItemTemplate>
    <asp:Label ID="lblImporte" runat="server" Text='<%# Eval("importe") %>'></asp:Label>
</EditItemTemplate>
<ItemTemplate>
    <asp:Label ID="lblImporte" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "importe", "{0:#,##0.00}") %>'></asp:Label>
</ItemTemplate>
<ItemStyle ForeColor="Red" />

Label lblImporte = (Label)gvTablaMes.Rows[e.RowIndex].FindControl("lblImporte");

lblImporte.ForeColor = System.Drawing.Color.Green;

gvTablaMes.Rows[e.RowIndex].Cells[X].ForeColor = System.Drawing.Color.Green;

protected void gvTablaMes_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if ((e.Row.RowState == DataControlRowState.Edit) || (e.Row.RowState == (DataControlRowState.Edit | DataControlRowState.Alternate)))
        {
            // the above checking is to verify whether the rows as well as alternating rows are in edit mode
            Label lblImporte = (Label)e.Row.FindControl("lblImporte");
            lblImporte.ForeColor = System.Drawing.Color.Green;
        }
    }

protected void Page_Load(object sender, EventArgs e)
{

    Label1.ForeColor = System.Drawing.Color.Orange;

}

<form id="form1" runat="server">
<div>

    <asp:Label ID="Label1" runat="server"></asp:Label>

</div>
</form>