Following How to use color in text with ReStructured Text (rst2html.py) or how to insert HTML tags without blank lines? I was able to set the background of the text within a table, like this:
.. role:: gbg
.. raw:: html
<style>
.gbg {background-color:#00ff00;}
</style>
+-------+----------------+-------+---------+-------+---------+
| UTC+1 | (d-s) | UTC-6 | (zo) | UTC-7 | (za) |
+=======+================+=======+=========+=======+=========+
| 15:00 | :gbg:`avail` | 8:00 | | 7:00 | |
+-------+ +-------+---------+-------+ +
| 15:30 | | 8:30 | | 7:30 | |
+-------+----------------+-------+---------+-------+---------+
That results in the word "avail" having a green background behind the letters, but how can I make the entire cell have a colored background instead of just the part of it behind those letters?