#3F7F7B

CSS

:root {
  --turquoise-tortoise: #3f7f7b;
  --turquoise-tortoise-rgb: 63 127 123;
  --turquoise-tortoise-oklch: oklch(0.553 0.066 190.1);
}

.element {
  color: var(--turquoise-tortoise);
  background-color: hsl(176 34% 37%);
  border-color: oklch(0.553 0.066 190.1);
}

Tailwind CSS v4

@theme {
  --color-turquoise-tortoise: #3f7f7b;
  --color-turquoise-tortoise-50: #e1fcfa;
  --color-turquoise-tortoise-100: #d0efed;
  --color-turquoise-tortoise-200: #b5dedb;
  --color-turquoise-tortoise-300: #90c3c0;
  --color-turquoise-tortoise-400: #6faba7;
  --color-turquoise-tortoise-500: #4c9490;
  --color-turquoise-tortoise-600: #427e7a;
  --color-turquoise-tortoise-700: #346461;
  --color-turquoise-tortoise-800: #254a47;
  --color-turquoise-tortoise-900: #193331;
  --color-turquoise-tortoise-950: #091f1d;
}

SCSS

$turquoise-tortoise: #3f7f7b;
$turquoise-tortoise-rgb: 63, 127, 123;
$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);
}