#00440A

CSS

:root {
  --british-racing-green: #00440a;
  --british-racing-green-rgb: 0 68 10;
  --british-racing-green-oklch: oklch(0.336 0.107 144.5);
}

.element {
  color: var(--british-racing-green);
  background-color: hsl(129 100% 13%);
  border-color: oklch(0.336 0.107 144.5);
}

Tailwind CSS v4

@theme {
  --color-british-racing-green: #00440a;
  --color-british-racing-green-50: #e2fee3;
  --color-british-racing-green-100: #d2f2d3;
  --color-british-racing-green-200: #b7e1ba;
  --color-british-racing-green-300: #93c797;
  --color-british-racing-green-400: #76af76;
  --color-british-racing-green-500: #569857;
  --color-british-racing-green-600: #49814a;
  --color-british-racing-green-700: #3a673b;
  --color-british-racing-green-800: #2b4c28;
  --color-british-racing-green-900: #1d351b;
  --color-british-racing-green-950: #0d200b;
}

SCSS

$british-racing-green: #00440a;
$british-racing-green-rgb: 0, 68, 10;
$british-racing-green-light: mix(#fff, $british-racing-green, 20%);
$british-racing-green-dark: mix(#000, $british-racing-green, 20%);

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