#5A7D74

CSS

:root {
  --underwater-world: #5a7d74;
  --underwater-world-rgb: 90 125 116;
  --underwater-world-oklch: oklch(0.56 0.042 177);
}

.element {
  color: var(--underwater-world);
  background-color: hsl(165 16% 42%);
  border-color: oklch(0.56 0.042 177);
}

Tailwind CSS v4

@theme {
  --color-underwater-world: #5a7d74;
  --color-underwater-world-50: #e9f9f5;
  --color-underwater-world-100: #daede8;
  --color-underwater-world-200: #c2dad4;
  --color-underwater-world-300: #a1bfb8;
  --color-underwater-world-400: #85a79e;
  --color-underwater-world-500: #689086;
  --color-underwater-world-600: #597a71;
  --color-underwater-world-700: #47615a;
  --color-underwater-world-800: #334741;
  --color-underwater-world-900: #23312d;
  --color-underwater-world-950: #121d1a;
}

SCSS

$underwater-world: #5a7d74;
$underwater-world-rgb: 90, 125, 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);
}