#637B78

CSS

:root {
  --underwater-world: #637b78;
  --underwater-world-rgb: 99 123 120;
  --underwater-world-oklch: oklch(0.563 0.028 187.1);
}

.element {
  color: var(--underwater-world);
  background-color: hsl(173 11% 44%);
  border-color: oklch(0.563 0.028 187.1);
}

Tailwind CSS v4

@theme {
  --color-underwater-world: #637b78;
  --color-underwater-world-50: #edf8f7;
  --color-underwater-world-100: #deebea;
  --color-underwater-world-200: #c7d8d7;
  --color-underwater-world-300: #a8bcba;
  --color-underwater-world-400: #8ca4a1;
  --color-underwater-world-500: #728d89;
  --color-underwater-world-600: #607774;
  --color-underwater-world-700: #4d5f5d;
  --color-underwater-world-800: #384644;
  --color-underwater-world-900: #26302f;
  --color-underwater-world-950: #141c1b;
}

SCSS

$underwater-world: #637b78;
$underwater-world-rgb: 99, 123, 120;
$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);
}