#557264

CSS

:root {
  --dark-forest: #557264;
  --dark-forest-rgb: 85 114 100;
  --dark-forest-oklch: oklch(0.525 0.04 163.8);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(151 15% 39%);
  border-color: oklch(0.525 0.04 163.8);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #557264;
  --color-dark-forest-50: #ebf9f2;
  --color-dark-forest-100: #dcece5;
  --color-dark-forest-200: #c5dad0;
  --color-dark-forest-300: #a5beb3;
  --color-dark-forest-400: #89a698;
  --color-dark-forest-500: #6e8f7f;
  --color-dark-forest-600: #5d796b;
  --color-dark-forest-700: #4a6156;
  --color-dark-forest-800: #36473e;
  --color-dark-forest-900: #25312b;
  --color-dark-forest-950: #131d18;
}

SCSS

$dark-forest: #557264;
$dark-forest-rgb: 85, 114, 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);
}