(Squarespace) Header multicolored border

[tuanphan]

To add multicolored border at bottom of header

You can use this code to Website > Website Tools > Custom CSS

header#header {
    border-bottom: 5px solid red;
}
header#header:after {
    content: "";
    position: absolute;
    bottom: -15px;
    left: 0;
    width: 100%;
    height: 5px;
    background-color: red;
}