Hey Credo,
the submenus can be coloured in custom colors by using this CSS:
#menu-item-XX a, #menu-item-XX .sub-menu .submenuline, #menu-item-XX .sub-menu li { background-color: #FFFFFF !important; }
where “XX” is the id of the menu item (you can look it up by using e.g. Chrome’s built-in code inspector (right-click and choose “Inspect element” on any part of the web page), and #FFFFFF is the hex color of your choice.
Regarding your second question: could you please provide the URL of the website in question, it is difficult to provide a definitive answer without seeing the code ;)
Sincerely,
Andrii / Satori Studio