The code for this is in the header.php file but you can add some custom css into the theme options panel for this:

.navigation-menu, .sf-vertical li, .jspDrag {background-color:#f20a0a;}

Just make it transparent instead of a color.

.navigation-menu, .sf-vertical li, .jspDrag {background:transparent;}

Thank you so much Mike

but i do that and i loss the color on cub MENU too, i would like to keep this one, just transparent for cube logo,
that is what i did,
/* MAIN BACKGROUND COLOUR FOR MENU AND LOGO */
.logo-menu, .navigation-menu, .sf-vertical li, .jspDrag {background:transparent;}
.sf-menu .current-menu-item a, .sf-menu a:hover, .sf-menu .current-menu-item .sliding-element a:hover {background:<?php echo of_get_option('menu_bg', "#f20a0a"); ?> url(<?php echo get_template_directory_uri(); ?>/images/nav-arrow.png) 0px 5px no-repeat;}
<?php echo '</style>'; ?>

what can i do?
thanks

Link? And what do you mean cub?