Colour Problem when hover over child items

At the moment, my main menu bar is yellow. If i leave the child items of the parent item yellow, when i hover over each child item, the child item changes to the hover color i have choosen (grey). (see picture 1)

However, i am hoping to create the following situation: The parent items are yellow. When i hover over the parent item, the child items are in black background (i know how to do this). When i hover over the child items, i can't get any hover colour working. As you can see from the picture 2, the parent items are yellow, the child items are black but there is no change in colour of hover items when i hover over them.

I was wondering if it is possible to have a hover color over the child items as mentioned in situation above? (i.e when hovering over child items in black, the child items turn to grey).