This way
<asp:Label ID="Label1" runat="server" Text="10"></asp:Label>
<asp:Label ID="Label2" runat="server" Text="12"></asp:Label>
protected void Page_Load(object sender, EventArgs e)
{
if (int.Parse(Label1.Text.Trim()) < int.Parse(Label2.Text.Trim()))
{
Label1.ForeColor = System.Drawing.Color.Red;
}
else
{
Label1.ForeColor = System.Drawing.Color.Black;
}
}