#637C74

CSS

:root {
  --underwater-world: #637c74;
  --underwater-world-rgb: 99 124 116;
  --underwater-world-oklch: oklch(0.564 0.032 173.7);
}

.element {
  color: var(--underwater-world);
  background-color: hsl(161 11% 44%);
  border-color: oklch(0.564 0.032 173.7);
}

Tailwind CSS v4

@theme {
  --color-underwater-world: #637c74;
  --color-underwater-world-50: #ecf8f5;
  --color-underwater-world-100: #deebe7;
  --color-underwater-world-200: #c7d9d3;
  --color-underwater-world-300: #a7bdb7;
  --color-underwater-world-400: #8ca59d;
  --color-underwater-world-500: #718d84;
  --color-underwater-world-600: #607870;
  --color-underwater-world-700: #4d605a;
  --color-underwater-world-800: #384641;
  --color-underwater-world-900: #26302d;
  --color-underwater-world-950: #141d1a;
}

SCSS

$underwater-world: #637c74;
$underwater-world-rgb: 99, 124, 116;
$underwater-world-light: mix(#fff, $underwater-world, 20%);
$underwater-world-dark: mix(#000, $underwater-world, 20%);

.element {
  color: $underwater-world;
  box-shadow: 0 0 0 2px rgba($underwater-world, 0.35);
}