next-app-template/components/Welcome/Welcome.module.scss

.title {
  color: light-dark(var(--mantine-color-black), var(--mantine-color-white));
  font-size: 100px;
  font-weight: 900;
  letter-spacing: -2px;

  @include dark {
    background-color: red;
  }

  @include light {
    background-color: blue;
  }

  @media (max-width: $mantine-breakpoint-md) {
    font-size: 50px;
  }
}