#647B78

CSS

:root {
  --underwater-world: #647b78;
  --underwater-world-rgb: 100 123 120;
  --underwater-world-oklch: oklch(0.564 0.027 186.7);
}

.element {
  color: var(--underwater-world);
  background-color: hsl(172 10% 44%);
  border-color: oklch(0.564 0.027 186.7);
}

Tailwind CSS v4

@theme {
  --color-underwater-world: #647b78;
  --color-underwater-world-50: #edf8f7;
  --color-underwater-world-100: #deebe9;
  --color-underwater-world-200: #c8d8d6;
  --color-underwater-world-300: #a9bcba;
  --color-underwater-world-400: #8da4a1;
  --color-underwater-world-500: #728c89;
  --color-underwater-world-600: #617774;
  --color-underwater-world-700: #4d5f5d;
  --color-underwater-world-800: #384643;
  --color-underwater-world-900: #26302f;
  --color-underwater-world-950: #151c1b;
}

SCSS

$underwater-world: #647b78;
$underwater-world-rgb: 100, 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);
}