#646D78

CSS

:root {
  --made-in-the-shade: #646d78;
  --made-in-the-shade-rgb: 100 109 120;
  --made-in-the-shade-oklch: oklch(0.531 0.02 253.5);
}

.element {
  color: var(--made-in-the-shade);
  background-color: hsl(213 9% 43%);
  border-color: oklch(0.531 0.02 253.5);
}

Tailwind CSS v4

@theme {
  --color-made-in-the-shade: #646d78;
  --color-made-in-the-shade-50: #f1f5fb;
  --color-made-in-the-shade-100: #e3e8ef;
  --color-made-in-the-shade-200: #cfd5dd;
  --color-made-in-the-shade-300: #b1b8c2;
  --color-made-in-the-shade-400: #969fab;
  --color-made-in-the-shade-500: #7d8794;
  --color-made-in-the-shade-600: #6a727d;
  --color-made-in-the-shade-700: #555c64;
  --color-made-in-the-shade-800: #3d4349;
  --color-made-in-the-shade-900: #2a2e33;
  --color-made-in-the-shade-950: #181b1f;
}

SCSS

$made-in-the-shade: #646d78;
$made-in-the-shade-rgb: 100, 109, 120;
$made-in-the-shade-light: mix(#fff, $made-in-the-shade, 20%);
$made-in-the-shade-dark: mix(#000, $made-in-the-shade, 20%);

.element {
  color: $made-in-the-shade;
  box-shadow: 0 0 0 2px rgba($made-in-the-shade, 0.35);
}