#5B7164

CSS

:root {
  --dark-forest: #5b7164;
  --dark-forest-rgb: 91 113 100;
  --dark-forest-oklch: oklch(0.527 0.033 159.1);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(145 11% 40%);
  border-color: oklch(0.527 0.033 159.1);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #5b7164;
  --color-dark-forest-50: #edf8f2;
  --color-dark-forest-100: #dfebe4;
  --color-dark-forest-200: #c9d9d0;
  --color-dark-forest-300: #a9bdb2;
  --color-dark-forest-400: #8fa597;
  --color-dark-forest-500: #748d7e;
  --color-dark-forest-600: #62776b;
  --color-dark-forest-700: #4f6055;
  --color-dark-forest-800: #39463e;
  --color-dark-forest-900: #27302b;
  --color-dark-forest-950: #151d18;
}

SCSS

$dark-forest: #5b7164;
$dark-forest-rgb: 91, 113, 100;
$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);
}