背景-单斜条纹

You just need to provide correct start and stop values for the colors. The occurrence of the multiple white stripes were due to the multiple #fff values that were used after 73.81%.

div {
  background: linear-gradient(135deg, #5cbcb0 5%, #ffffff 5%, #ffffff 15%, #5cbcb0 15%);
  /* Start #5cbcb0 from 0 and end at 5%, Start #fff at 5% and end at 15%, Start #5cbcb0 again at 15% and end at 100% */
  background-size: 593.97px 593.97px;
  background-repeat: no-repeat; /* To avoid multiple instances */
}