#5A716D

CSS

:root {
  --dark-forest: #5a716d;
  --dark-forest-rgb: 90 113 109;
  --dark-forest-oklch: oklch(0.529 0.028 183.5);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(170 11% 40%);
  border-color: oklch(0.529 0.028 183.5);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #5a716d;
  --color-dark-forest-50: #edf8f6;
  --color-dark-forest-100: #deebe9;
  --color-dark-forest-200: #c8d8d6;
  --color-dark-forest-300: #a8bcb9;
  --color-dark-forest-400: #8da4a0;
  --color-dark-forest-500: #728d88;
  --color-dark-forest-600: #617773;
  --color-dark-forest-700: #4d5f5c;
  --color-dark-forest-800: #384643;
  --color-dark-forest-900: #26302e;
  --color-dark-forest-950: #151c1b;
}

SCSS

$dark-forest: #5a716d;
$dark-forest-rgb: 90, 113, 109;
$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);
}