#557618

CSS

:root {
  --over-the-hills: #557618;
  --over-the-hills-rgb: 85 118 24;
  --over-the-hills-oklch: oklch(0.522 0.124 127.6);
}

.element {
  color: var(--over-the-hills);
  background-color: hsl(81 66% 28%);
  border-color: oklch(0.522 0.124 127.6);
}

Tailwind CSS v4

@theme {
  --color-over-the-hills: #557618;
  --color-over-the-hills-50: #eafdd8;
  --color-over-the-hills-100: #dbf1c5;
  --color-over-the-hills-200: #c3dfa7;
  --color-over-the-hills-300: #a3c480;
  --color-over-the-hills-400: #8aac59;
  --color-over-the-hills-500: #6f952f;
  --color-over-the-hills-600: #5e7e29;
  --color-over-the-hills-700: #4b6521;
  --color-over-the-hills-800: #384a14;
  --color-over-the-hills-900: #26330c;
  --color-over-the-hills-950: #151f01;
}

SCSS

$over-the-hills: #557618;
$over-the-hills-rgb: 85, 118, 24;
$over-the-hills-light: mix(#fff, $over-the-hills, 20%);
$over-the-hills-dark: mix(#000, $over-the-hills, 20%);

.element {
  color: $over-the-hills;
  box-shadow: 0 0 0 2px rgba($over-the-hills, 0.35);
}