mdb-ui-kit/scss/includes/_switch.scss

.switch {
  vertical-align: middle;
  &, label, input, .switch-decorator {
    user-select: none;
  }
  label {
    cursor: pointer;
    color: $mdb-switch-label-color;

    // Hide original checkbox
    input[type=checkbox] {
      opacity: 0;
      width: 0;
      height: 0;
    }
    // Switch bg off and disabled
    .switch-decorator,
    input[type=checkbox][disabled] + .switch-decorator {
      content: "";
      display: inline-block;
      width: 30px;
      height: 15px;
      background-color: rgba(80, 80, 80, 0.7);
      border-radius: 15px;
      margin-right: 15px;
      transition: background 0.3s ease;
      vertical-align: middle;
    }
    // Handle off
    .switch-decorator:after {
      content: "";
      display: inline-block;
      width: 20px;
      height: 20px;
      background-color: #F1F1F1;
      border-radius: 20px;
      position: relative;
      box-shadow: 0 1px 3px 1px rgba(0, 0, 0, 0.4);
      left: -5px;
      top: -2px;
      transition: left 0.3s ease, background 0.3s ease, box-shadow 0.1s ease;
    }
    input[type=checkbox] {
      // Handle disabled
      &[disabled] {
        & + .switch-decorator:after,
        &:checked + .switch-decorator:after {
          background-color: #BDBDBD;
        }
      }

      & + .switch-decorator:active:after,
      &[disabled] + .switch-decorator:active:after {
        box-shadow: 0 1px 3px 1px rgba(0, 0, 0, 0.4), 0 0 0 15px rgba(0, 0, 0, 0.1);
      }

      // Ripple off and disabled
      &:checked + .switch-decorator:after {
        left: 15px;
      }
    }

    & label input[type=checkbox]:checked {
      & + .switch-decorator {
        background-color: rgba($brand-primary, (50/100)); // Switch bg on
      }

      & + .switch-decorator:after {
        background-color: $brand-primary; // Handle on
      }

      & + .switch-decorator:active:after {
        box-shadow: 0 1px 3px 1px rgba(0, 0, 0, 0.4), 0 0 0 15px rgba($brand-primary, (10/100)); // Ripple on
      }
    }
  }
}