#57716D

CSS

:root {
  --dark-forest: #57716d;
  --dark-forest-rgb: 87 113 109;
  --dark-forest-oklch: oklch(0.527 0.031 184.7);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(171 13% 39%);
  border-color: oklch(0.527 0.031 184.7);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #57716d;
  --color-dark-forest-50: #ecf8f6;
  --color-dark-forest-100: #ddebe9;
  --color-dark-forest-200: #c6d9d6;
  --color-dark-forest-300: #a6bdba;
  --color-dark-forest-400: #8ba5a1;
  --color-dark-forest-500: #708d89;
  --color-dark-forest-600: #5f7774;
  --color-dark-forest-700: #4c605c;
  --color-dark-forest-800: #374643;
  --color-dark-forest-900: #25302e;
  --color-dark-forest-950: #141d1b;
}

SCSS

$dark-forest: #57716d;
$dark-forest-rgb: 87, 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);
}