I was able to figure this out but not completely filling in the cell with the desired color.
I changed the unboundfield to the following:
<igtbl:TemplateDataField Key="tabcolor" Header-Text="Color" Header-Tooltip="Color" CssClass="NoPaddingCssClass">
<ItemTemplate>
<asp:Panel ID="CellColorPanel" runat="server" Width="100%" Height="100%" />
</ItemTemplate>
</igtbl:TemplateDataField>
In the CssClass, I set the following properties:
.NoPaddingCssClass
{
padding: 0px 0px 0px 0px;
margin: 0px 0px 0px 0px;
}
This leaves me with a small white border around the panel that I can't get to go away, is there some css that I'm missing?