Hi slb2013,

Please refer below sample.

HTML

Default

<uc:Signal runat="server" ID="ucSignal" />

User Control

<%foreach (Signal message in this.SignalData)
  {%>
<span class='<%=message.SignalStrength=="Pass"?"Green":"Red" %>'>
    <%=message.SignalStrength%></span><br />
<%} %>
<style type="text/css">
    .Green
    {
        font-family: Arial;
        font-size: 10pt;
        color: green;
    }
    .Red
    {
        font-family: Arial;
        font-size: 10pt;
        color: red;
    }
</style>

Signal Class

C#

public class Signal
{
    public string SignalStrength { get; set; }
    public int Percent { get; set; }
}

Code

UserControl

public List<Signal> SignalData { get; set; }

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        ucSignal.SignalData = new List<Signal>()
        {
            new Signal{ SignalStrength="Fail",Percent=10},
            new Signal{ SignalStrength="Pass",Percent=80},
        };
    }
}

 Screenshot