Module:Diff/styles.css

.mdl-diff {
    width: 100%;
    box-sizing: border-box;
}

.mdl-diff-marker {
    width: 2%;
    display: inline-block;
    padding: 0.25em;
    font-weight: bold;
    font-size: 1.25em;
    text-align: end;
}

.mdl-diff-deletedline {
    border-color: #ffe49c;
}

.mdl-diff-addedline {
    border-color: #a3d3ff;
}

div.mdl-diff-div {
    word-wrap: break-word;
    direction: ltr;
}

.mdl-diff-change-inline {
    color: inherit;
    padding: 0.25em 0;
    font-weight: bold;
    text-decoration: initial;
}

.mdl-diff-changedline {
    vertical-align: top;
    width: 48%;
    border-style: solid;
    border-radius: 0.33em;
    padding: 0.33em 0.5em;
    color: inherit;
    font-size: 1em;
    white-space: pre-wrap;
    border-width: 1px 1px 1px 4px;
}