#5A7167

CSS

:root {
  --dark-forest: #5a7167;
  --dark-forest-rgb: 90 113 103;
  --dark-forest-oklch: oklch(0.527 0.031 166.9);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(154 11% 40%);
  border-color: oklch(0.527 0.031 166.9);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #5a7167;
  --color-dark-forest-50: #edf8f3;
  --color-dark-forest-100: #deebe6;
  --color-dark-forest-200: #c8d9d2;
  --color-dark-forest-300: #a9bdb4;
  --color-dark-forest-400: #8ea59a;
  --color-dark-forest-500: #738d82;
  --color-dark-forest-600: #61776e;
  --color-dark-forest-700: #4e6058;
  --color-dark-forest-800: #394640;
  --color-dark-forest-900: #27302c;
  --color-dark-forest-950: #151d19;
}

SCSS

$dark-forest: #5a7167;
$dark-forest-rgb: 90, 113, 103;
$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);
}