Question

Answer 1

В ксс, background

nav ul ul {
background: 0px 0px #E51A1A;
left: -1px;
opacity: 0;
position: absolute;
text-align: left;
top: 100%;
transition: all 0.2s cubic-bezier(0, 0, 0.58, 1) 0.15s;
visibility: hidden;
white-space: nowrap;
z-index: 1;
}