have You used external css?
if yes then check th, td color property is'nt set in css ?
or
try this
<asp:TemplateField ItemStyle-Height ="10px">
<ItemTemplate>
<asp:CommandField meta:resourcekey="CommandFieldResource1"
ShowSelectButton="True" />
</ItemTemplate>
<HeaderStyle HorizontalAlign="Left" CssClass="HeaderStyle1" />
<ItemStyle Width="10px" />
</asp:TemplateField>
and in css
td.HeaderStyle1
{
text-decoration:none;
color:#ffffff;
font-weight:bold;
font-size:12px;
height:30px;
border :0px;
}