Try to use the <font>
tag
?<table>
<thead>
<tr>
<th><font color="#FFF">Header 1</font></th>
<th><font color="#FFF">Header 1</font></th>
<th><font color="#FFF">Header 1</font></th>
</tr>
</thead>
<tbody>
<tr>
<td>blah blah</td>
<td>blah blah</td>
<td>blah blah</td>
</tr>
</tbody>
</table>
But I think this should work, too:
?<table>
<thead>
<tr>
<th color="#FFF">Header 1</th>
<th color="#FFF">Header 1</th>
<th color="#FFF">Header 1</th>
</tr>
</thead>
<tbody>
<tr>
<td>blah blah</td>
<td>blah blah</td>
<td>blah blah</td>
</tr>
</tbody>
</table>
EDIT:
Crossbrowser solution:
use capitals in HEX-color.
<th bgcolor="#5D7B9D" color="#FFFFFF"><font color="#FFFFFF">Header 1</font></th>