You can get the old colors by adding to your personal css the following:

td.diff-addedline {
background: #cfc;
border: 0;
}
td.diff-deletedline {
background: #ffa;
border: 0;
}
td.diff-context {
background: #eee;
border: 0;
}
td.diff-addedline .diffchange, td.diff-deletedline .diffchange {
color: red;
background: inherit;
}