#597168

CSS

:root {
  --dark-forest: #597168;
  --dark-forest-rgb: 89 113 104;
  --dark-forest-oklch: oklch(0.527 0.032 170.2);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(158 12% 40%);
  border-color: oklch(0.527 0.032 170.2);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #597168;
  --color-dark-forest-50: #edf8f4;
  --color-dark-forest-100: #deebe7;
  --color-dark-forest-200: #c7d9d3;
  --color-dark-forest-300: #a8bdb5;
  --color-dark-forest-400: #8da59c;
  --color-dark-forest-500: #728d83;
  --color-dark-forest-600: #61786f;
  --color-dark-forest-700: #4d6059;
  --color-dark-forest-800: #384640;
  --color-dark-forest-900: #26302c;
  --color-dark-forest-950: #151d19;
}

SCSS

$dark-forest: #597168;
$dark-forest-rgb: 89, 113, 104;
$dark-forest-light: mix(#fff, $dark-forest, 20%);
$dark-forest-dark: mix(#000, $dark-forest, 20%);

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