One of the main issues with HTML on Interlude is that you can only have a few very specific basic colors and nothing in-between.
However, there is an approach you can take to make it so that you have custom colors for your table background.
To do this, you would have to stack a bunch of tables with different background colors.
Here is an example of the code:
HTML:
<table width="274" cellpadding="0" cellspacing="0" height="32" border="0" bgcolor="FF0000">
<tr>
<td...