That's one of the joys of using CSS to set a table's appearance. Wonderful control over background, borders, etc, by cell, row or overall. And that allows all kinds of special effects - such as a border just around the table instead of intruding between the individual cells.
You can also set <tr style="background-color: rgb(123, 123, 123);" > if you want to have separate colors for each row. However color in td is more important for the browser, so it will cover the color specified in td.