<div class="swatch"></div>
<div class="swatch"></div>
<div class="swatch primary"></div>
<div class="swatch"></div>
<div class="swatch"></div>

@layer demo {
  :root {
    --base-color: deeppink; /* change me */
  }
  
  .swatch:nth-child(1) {
    background: oklch(from var(--base-color) calc(l - 20) c h);
  }
  
  .swatch:nth-child(2) {
    background: oklch(from var(--base-color) calc(l - 10) c h);
  }
  
  .swatch.primary {
    background: var(--base-color);
  }
  
  .swatch:nth-child(4) {
    background: oklch(from var(--base-color) calc(l + 10) c h);
  }
  
  .swatch:nth-child(5) {
    background: oklch(from var(--base-color) calc(l + 20) c h);
  }
}

@layer demo.support {
  * {
    box-sizing: border-box;
    margin: 0;
  }

  html {
    block-size: 100%;
    color-scheme: dark light;
  }

  body {
    min-block-size: 100%;
    font-family: system-ui, sans-serif;

    display: grid;
    grid-template-rows: repeat(5, 1fr);
  }
}