#636D78

CSS

:root {
  --made-in-the-shade: #636d78;
  --made-in-the-shade-rgb: 99 109 120;
  --made-in-the-shade-oklch: oklch(0.53 0.021 250.8);
}

.element {
  color: var(--made-in-the-shade);
  background-color: hsl(211 10% 43%);
  border-color: oklch(0.53 0.021 250.8);
}

Tailwind CSS v4

@theme {
  --color-made-in-the-shade: #636d78;
  --color-made-in-the-shade-50: #f1f6fb;
  --color-made-in-the-shade-100: #e3e8ef;
  --color-made-in-the-shade-200: #ced5dd;
  --color-made-in-the-shade-300: #b0b8c2;
  --color-made-in-the-shade-400: #95a0ab;
  --color-made-in-the-shade-500: #7c8894;
  --color-made-in-the-shade-600: #69737d;
  --color-made-in-the-shade-700: #545c64;
  --color-made-in-the-shade-800: #3d434a;
  --color-made-in-the-shade-900: #2a2e33;
  --color-made-in-the-shade-950: #171b1f;
}

SCSS

$made-in-the-shade: #636d78;
$made-in-the-shade-rgb: 99, 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);
}