You have to add a class to scope the CSS, then add the styles to the global styles file in the angular project.

SCSS:

.custom-button > button {
  background: rgb(46, 82, 33) ;
  background: linear-gradient(
    90deg,
    rgba(46, 82, 33, 1) 22%,
    rgba(104, 157, 79, 1) 100%
  ) ;
}

.custom-switch {
  .p-inputswitch .p-inputswitch-slider {
    background: black;
  }
}

HTML:

<div class="card flex justify-content-center">
  <p-button label="Submit" class="custom-button" />
  <p-inputSwitch class="custom-switch" />
</div>

Stackblitz Demo