How to change the background colour for nav-bar dropdown menu?

Im trying to expand the size of the dropdown menu but most of all im trying to change the background colour, I can only seem to change the colour of the links and the area around the links.

.dropdown-menu .dropdown-item {
text-align: left;
background-color: aqua;
}

.dropdown-menu a {
color: rgb(48, 58, 78);
}

.dropdown-menu > a:hover {
background-image: none;
background-color: rgb(255, 255, 255);
text-align: center;
}

This is the dropdown menu. I want to colour in the white, and expand the size of the dropdown menu. If this is possible, what should I do?