Демо CSS: linear-gradient()

background: linear-gradient(#e66465, #9198e5);

background: linear-gradient(0.25turn, #3f87a6, #ebf8e1, #f69d3c);

background: linear-gradient(to left, #333, #333 50%, #eee 75%, #333 75%);

background: linear-gradient(217deg, rgba(255,0,0,.8), rgba(255,0,0,0) 70.71%),
              linear-gradient(127deg, rgba(0,255,0,.8), rgba(0,255,0,0) 70.71%),
              linear-gradient(336deg, rgba(0,0,255,.8), rgba(0,0,255,0) 70.71%);