#637974

CSS

:root {
  --underwater-world: #637974;
  --underwater-world-rgb: 99 121 116;
  --underwater-world-oklch: oklch(0.557 0.027 179.9);
}

.element {
  color: var(--underwater-world);
  background-color: hsl(166 10% 43%);
  border-color: oklch(0.557 0.027 179.9);
}

Tailwind CSS v4

@theme {
  --color-underwater-world: #637974;
  --color-underwater-world-50: #edf8f6;
  --color-underwater-world-100: #dfebe8;
  --color-underwater-world-200: #c8d8d5;
  --color-underwater-world-300: #a9bcb8;
  --color-underwater-world-400: #8ea49f;
  --color-underwater-world-500: #738c87;
  --color-underwater-world-600: #627772;
  --color-underwater-world-700: #4e5f5b;
  --color-underwater-world-800: #394642;
  --color-underwater-world-900: #27302e;
  --color-underwater-world-950: #151c1b;
}

SCSS

$underwater-world: #637974;
$underwater-world-rgb: 99, 121, 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);
}