#5A716B

CSS

:root {
  --dark-forest: #5a716b;
  --dark-forest-rgb: 90 113 107;
  --dark-forest-oklch: oklch(0.528 0.029 177.5);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(164 11% 40%);
  border-color: oklch(0.528 0.029 177.5);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #5a716b;
  --color-dark-forest-50: #edf8f5;
  --color-dark-forest-100: #deebe8;
  --color-dark-forest-200: #c8d8d4;
  --color-dark-forest-300: #a8bcb8;
  --color-dark-forest-400: #8da49e;
  --color-dark-forest-500: #738d86;
  --color-dark-forest-600: #617771;
  --color-dark-forest-700: #4d5f5b;
  --color-dark-forest-800: #384642;
  --color-dark-forest-900: #26302d;
  --color-dark-forest-950: #151d1a;
}

SCSS

$dark-forest: #5a716b;
$dark-forest-rgb: 90, 113, 107;
$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);
}