#557D6F

CSS

:root {
  --turquoise-tortoise: #557d6f;
  --turquoise-tortoise-rgb: 85 125 111;
  --turquoise-tortoise-oklch: oklch(0.556 0.05 170.6);
}

.element {
  color: var(--turquoise-tortoise);
  background-color: hsl(159 19% 41%);
  border-color: oklch(0.556 0.05 170.6);
}

Tailwind CSS v4

@theme {
  --color-turquoise-tortoise: #557d6f;
  --color-turquoise-tortoise-50: #e8faf4;
  --color-turquoise-tortoise-100: #d8eee6;
  --color-turquoise-tortoise-200: #c0dcd2;
  --color-turquoise-tortoise-300: #9ec0b5;
  --color-turquoise-tortoise-400: #81a89a;
  --color-turquoise-tortoise-500: #649181;
  --color-turquoise-tortoise-600: #557b6e;
  --color-turquoise-tortoise-700: #446258;
  --color-turquoise-tortoise-800: #31483f;
  --color-turquoise-tortoise-900: #21322c;
  --color-turquoise-tortoise-950: #111e19;
}

SCSS

$turquoise-tortoise: #557d6f;
$turquoise-tortoise-rgb: 85, 125, 111;
$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);
}