Should be the following. By using the method find on the table class, you can ensure that any other fields which happen to have the same class name are not included. Or just use a unique class name for your table fields and reference them directly. A class defined on a table field effects the entire column.
The !important is also important, specifying to override any built in style definitions
Changing the text color to white is usually required too, if your trying to make a field stand out with solid RGB colors.
$('.tableClass').find('.fieldClassName input').attr('style', 'background-color: #6699ff !important; color:white;');