#66AC3F

CSS

:root {
  --grass: #66ac3f;
  --grass-rgb: 102 172 63;
  --grass-oklch: oklch(0.675 0.16 136.1);
}

.element {
  color: var(--grass);
  background-color: hsl(99 46% 46%);
  border-color: oklch(0.675 0.16 136.1);
}

Tailwind CSS v4

@theme {
  --color-grass: #66ac3f;
  --color-grass-50: #dfffd4;
  --color-grass-100: #cef5c1;
  --color-grass-200: #b3e5a2;
  --color-grass-300: #8ecb79;
  --color-grass-400: #71b34d;
  --color-grass-500: #4f9c17;
  --color-grass-600: #448418;
  --color-grass-700: #366a14;
  --color-grass-800: #294e07;
  --color-grass-900: #1c3605;
  --color-grass-950: #0c2100;
}

SCSS

$grass: #66ac3f;
$grass-rgb: 102, 172, 63;
$grass-light: mix(#fff, $grass, 20%);
$grass-dark: mix(#000, $grass, 20%);

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