#133028

CSS

:root {
  --swamp-thing: #133028;
  --swamp-thing-rgb: 19 48 40;
  --swamp-thing-oklch: oklch(0.284 0.038 173.2);
}

.element {
  color: var(--swamp-thing);
  background-color: hsl(163 43% 13%);
  border-color: oklch(0.284 0.038 173.2);
}

Tailwind CSS v4

@theme {
  --color-swamp-thing: #133028;
  --color-swamp-thing-50: #ebf9f4;
  --color-swamp-thing-100: #dbece7;
  --color-swamp-thing-200: #c4dad3;
  --color-swamp-thing-300: #a4beb6;
  --color-swamp-thing-400: #88a69c;
  --color-swamp-thing-500: #6c8f84;
  --color-swamp-thing-600: #5c7970;
  --color-swamp-thing-700: #496159;
  --color-swamp-thing-800: #354741;
  --color-swamp-thing-900: #24312c;
  --color-swamp-thing-950: #131d1a;
}

SCSS

$swamp-thing: #133028;
$swamp-thing-rgb: 19, 48, 40;
$swamp-thing-light: mix(#fff, $swamp-thing, 20%);
$swamp-thing-dark: mix(#000, $swamp-thing, 20%);

.element {
  color: $swamp-thing;
  box-shadow: 0 0 0 2px rgba($swamp-thing, 0.35);
}