matrix.org/sass/_legacy-docs.scss

.legacy-doc-warning {
    padding: 1rem;
    border-radius: .5rem;
    background-color: #F6E7D5;
    color: #6F420F;
    margin-top: 1rem;
    margin-bottom: 1rem;

    h2 {
        margin-top: 0px;
        margin-bottom: 10px;
    }

    &.outdated {
        background-color: #F6D5D5;
        color: #8B1212;
    }
}