Sorry, my fault - it could not work because there's still "white" set as background for the table as such, and I've not included that in the theme options.
Please find in style.css.php (should be line 1183-1187):
HTML Code:
.post table {
border-collapse: collapse;
background-color: #ffffff;
margin: 10px 0;
}
and delete the line with "background-color"
I am also removing that from style.css for the next theme version