From Alan Lepofsky:
Each tab's color is the same as the background color for each row. However, you may not want the contents of each tab to have the background colour, so what I do is insert another 1*1 table with a white background, and fit the margins to 1% and 99%.
From Ben Langhinrichs:
Set the tabs to different colors (make sure there is only one column), and set all the cell borders to 0. Next, inside each tab, create a nested table which has a background color of white. A nice little touch I like to do is to have the cell borders on for the inside table, but change the cell border color to that of the tab.