#5A716A

CSS

:root {
  --dark-forest: #5a716a;
  --dark-forest-rgb: 90 113 106;
  --dark-forest-oklch: oklch(0.528 0.029 174.7);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(162 11% 40%);
  border-color: oklch(0.528 0.029 174.7);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #5a716a;
  --color-dark-forest-50: #edf8f5;
  --color-dark-forest-100: #deebe7;
  --color-dark-forest-200: #c8d9d4;
  --color-dark-forest-300: #a9bdb7;
  --color-dark-forest-400: #8da49d;
  --color-dark-forest-500: #738d85;
  --color-dark-forest-600: #617770;
  --color-dark-forest-700: #4e5f5a;
  --color-dark-forest-800: #384641;
  --color-dark-forest-900: #27302d;
  --color-dark-forest-950: #151d1a;
}

SCSS

$dark-forest: #5a716a;
$dark-forest-rgb: 90, 113, 106;
$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);
}