#537E78

CSS

:root {
  --turquoise-tortoise: #537e78;
  --turquoise-tortoise-rgb: 83 126 120;
  --turquoise-tortoise-oklch: oklch(0.56 0.049 185);
}

.element {
  color: var(--turquoise-tortoise);
  background-color: hsl(172 21% 41%);
  border-color: oklch(0.56 0.049 185);
}

Tailwind CSS v4

@theme {
  --color-turquoise-tortoise: #537e78;
  --color-turquoise-tortoise-50: #e7faf7;
  --color-turquoise-tortoise-100: #d7edea;
  --color-turquoise-tortoise-200: #bedbd8;
  --color-turquoise-tortoise-300: #9cc0bb;
  --color-turquoise-tortoise-400: #7ea8a2;
  --color-turquoise-tortoise-500: #61918a;
  --color-turquoise-tortoise-600: #527b75;
  --color-turquoise-tortoise-700: #41625e;
  --color-turquoise-tortoise-800: #2f4844;
  --color-turquoise-tortoise-900: #20322f;
  --color-turquoise-tortoise-950: #0f1e1b;
}

SCSS

$turquoise-tortoise: #537e78;
$turquoise-tortoise-rgb: 83, 126, 120;
$turquoise-tortoise-light: mix(#fff, $turquoise-tortoise, 20%);
$turquoise-tortoise-dark: mix(#000, $turquoise-tortoise, 20%);

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