#557266

CSS

:root {
  --dark-forest: #557266;
  --dark-forest-rgb: 85 114 102;
  --dark-forest-oklch: oklch(0.526 0.039 167.5);
}

.element {
  color: var(--dark-forest);
  background-color: hsl(155 15% 39%);
  border-color: oklch(0.526 0.039 167.5);
}

Tailwind CSS v4

@theme {
  --color-dark-forest: #557266;
  --color-dark-forest-50: #ebf9f3;
  --color-dark-forest-100: #dcece6;
  --color-dark-forest-200: #c5dad1;
  --color-dark-forest-300: #a5beb4;
  --color-dark-forest-400: #89a69a;
  --color-dark-forest-500: #6e8f81;
  --color-dark-forest-600: #5d796d;
  --color-dark-forest-700: #4a6157;
  --color-dark-forest-800: #36473f;
  --color-dark-forest-900: #25312b;
  --color-dark-forest-950: #131d19;
}

SCSS

$dark-forest: #557266;
$dark-forest-rgb: 85, 114, 102;
$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);
}