Hey,
1) Yes - open up css/custom.css and add following code. Adjust the padding value:
.main_menu .avia_mega1, .main_menu .avia_mega2, .main_menu .avia_mega3, .main_menu .avia_mega4, .main_menu .avia_mega5 {
padding: 8px;
}
2) Yes - by default following image is used as nav item icon: http://www.wenv-verzekeringen.be/beta/wp-content/themes/brightbox/images/skin1/menu_arrow.png
You can replace the image or change the image source by using following code in css/custom.css:
#top .main_menu .avia_mega ul ul li, #top .main_menu .avia_mega > li > ul li {
background-image: url("../images/skin1/menu_arrow.png");
}
3) Yes - use following code:
#menu-item-742, #menu-item-743{
color: #ff000 !important;
}