Transparent background for Hot Caroussel and Menus

I tried to apply in template settings for the left or right module a transparent background.
In joomla version 3.0 i just inserted instead of the color code "background-transparent".
In version 3.1.1 it is not possible anymore to type code into the field. Same for the background in HOT Caroussel.
Is there a piece of code I can add somewhere for both areas or is there a "color code" for transparant background?

You can ad css to bottom of template_css.css:


.column_left_top {
background: transparent!important;
}

.column_right_top {
background: transparent!important;
}