styles.css

.content {
  /* background: #FFEEEE;*/
  /* background: -webkit-linear-gradient(to right, #DDEFBB, #FFEEEE);*/
  /* background: linear-gradient(to right, #DDEFBB, #FFEEEE);*/
  background: #43C6AC;  /* fallback for old browsers */
  background: -webkit-linear-gradient(to right, #F8FFAE, #43C6AC);  /* Chrome 10-25, Safari 5.1-6 */
  background: linear-gradient(to right, #F8FFAE, #43C6AC); /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */
}

.panel-header {
  color: black;
}

.panel {
  background: rgba(150, 150, 150, 0.5);
}