#42756F

CSS

:root {
  --turquoise-tortoise: #42756f;
  --turquoise-tortoise-rgb: 66 117 111;
  --turquoise-tortoise-oklch: oklch(0.525 0.056 186);
}

.element {
  color: var(--turquoise-tortoise);
  background-color: hsl(173 28% 36%);
  border-color: oklch(0.525 0.056 186);
}

Tailwind CSS v4

@theme {
  --color-turquoise-tortoise: #42756f;
  --color-turquoise-tortoise-50: #e4fbf8;
  --color-turquoise-tortoise-100: #d4eeeb;
  --color-turquoise-tortoise-200: #badcd8;
  --color-turquoise-tortoise-300: #97c1bd;
  --color-turquoise-tortoise-400: #78aaa3;
  --color-turquoise-tortoise-500: #59938c;
  --color-turquoise-tortoise-600: #4c7c76;
  --color-turquoise-tortoise-700: #3c635e;
  --color-turquoise-tortoise-800: #2b4944;
  --color-turquoise-tortoise-900: #1d332f;
  --color-turquoise-tortoise-950: #0d1e1c;
}

SCSS

$turquoise-tortoise: #42756f;
$turquoise-tortoise-rgb: 66, 117, 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);
}