#5A7B74

CSS

:root {
  --underwater-world: #5a7b74;
  --underwater-world-rgb: 90 123 116;
  --underwater-world-oklch: oklch(0.555 0.039 180.2);
}

.element {
  color: var(--underwater-world);
  background-color: hsl(167 15% 42%);
  border-color: oklch(0.555 0.039 180.2);
}

Tailwind CSS v4

@theme {
  --color-underwater-world: #5a7b74;
  --color-underwater-world-50: #eaf9f6;
  --color-underwater-world-100: #daece9;
  --color-underwater-world-200: #c3dad5;
  --color-underwater-world-300: #a2beb9;
  --color-underwater-world-400: #86a69f;
  --color-underwater-world-500: #6a8f87;
  --color-underwater-world-600: #5a7972;
  --color-underwater-world-700: #48615b;
  --color-underwater-world-800: #344742;
  --color-underwater-world-900: #23312e;
  --color-underwater-world-950: #121d1b;
}

SCSS

$underwater-world: #5a7b74;
$underwater-world-rgb: 90, 123, 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);
}