#39747F

CSS

:root {
  --mysterious-blue: #39747f;
  --mysterious-blue-rgb: 57 116 127;
  --mysterious-blue-oklch: oklch(0.524 0.064 211.2);
}

.element {
  color: var(--mysterious-blue);
  background-color: hsl(189 38% 36%);
  border-color: oklch(0.524 0.064 211.2);
}

Tailwind CSS v4

@theme {
  --color-mysterious-blue: #39747f;
  --color-mysterious-blue-50: #e2faff;
  --color-mysterious-blue-100: #d1eef5;
  --color-mysterious-blue-200: #b6dce5;
  --color-mysterious-blue-300: #92c0cb;
  --color-mysterious-blue-400: #71a9b4;
  --color-mysterious-blue-500: #50929e;
  --color-mysterious-blue-600: #447b86;
  --color-mysterious-blue-700: #36636b;
  --color-mysterious-blue-800: #26494e;
  --color-mysterious-blue-900: #193236;
  --color-mysterious-blue-950: #0a1e21;
}

SCSS

$mysterious-blue: #39747f;
$mysterious-blue-rgb: 57, 116, 127;
$mysterious-blue-light: mix(#fff, $mysterious-blue, 20%);
$mysterious-blue-dark: mix(#000, $mysterious-blue, 20%);

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