#5B4736

CSS

:root {
  --turtle: #5b4736;
  --turtle-rgb: 91 71 54;
  --turtle-oklch: oklch(0.414 0.038 61.8);
}

.element {
  color: var(--turtle);
  background-color: hsl(28 26% 28%);
  border-color: oklch(0.414 0.038 61.8);
}

Tailwind CSS v4

@theme {
  --color-turtle: #5b4736;
  --color-turtle-50: #fdf3ea;
  --color-turtle-100: #f1e5db;
  --color-turtle-200: #e0d1c4;
  --color-turtle-300: #c6b4a4;
  --color-turtle-400: #b09a88;
  --color-turtle-500: #99816c;
  --color-turtle-600: #826d5c;
  --color-turtle-700: #685749;
  --color-turtle-800: #4d3f35;
  --color-turtle-900: #352c24;
  --color-turtle-950: #201913;
}

SCSS

$turtle: #5b4736;
$turtle-rgb: 91, 71, 54;
$turtle-light: mix(#fff, $turtle, 20%);
$turtle-dark: mix(#000, $turtle, 20%);

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