formating table transparent

Giganews Newsgroups
Subject: formating table transparent
Posted by:  pfei… (Markus Pfeifenberger -
Date: 30 Jul 2004

i have the following problem:
in the css file i format the <td> background of a <table> default as
td { background-color : #FF0000;}

is it possible and if yes how to define a class of td, lets say
td.trans , where the red background is overruled as transparent?

td.trans {background-color : ???;}

Thanks Markus