demo scss

demo.css

.list {
  background-image: url(xxx.png);
}

.header {
  margin-bottom: 20px;
  -webkit-transform: rotateZ(135deg);
          transform: rotateZ(135deg);
}

.list {
  width: 100px;
  background-color: #0C355F;
  background-position: 0 0;
}

demo.scss

$blue: #0C355F;
%bg {
    background-image: url(xxx.png);
}
.header {
    margin-bottom: 20px;
    transform: rotateZ(135deg);
}
.list {
    width: 100px;
    background-color: $blue;
    @extend %bg;
    background-position: 0 0;
}