#427F8A

CSS

:root {
  --mysterious-blue: #427f8a;
  --mysterious-blue-rgb: 66 127 138;
  --mysterious-blue-oklch: oklch(0.56 0.065 210.6);
}

.element {
  color: var(--mysterious-blue);
  background-color: hsl(189 35% 40%);
  border-color: oklch(0.56 0.065 210.6);
}

Tailwind CSS v4

@theme {
  --color-mysterious-blue: #427f8a;
  --color-mysterious-blue-50: #e1fbff;
  --color-mysterious-blue-100: #d0eef5;
  --color-mysterious-blue-200: #b5dce5;
  --color-mysterious-blue-300: #91c1cb;
  --color-mysterious-blue-400: #70a9b4;
  --color-mysterious-blue-500: #4d929e;
  --color-mysterious-blue-600: #427c86;
  --color-mysterious-blue-700: #35636b;
  --color-mysterious-blue-800: #25494e;
  --color-mysterious-blue-900: #193237;
  --color-mysterious-blue-950: #091e21;
}

SCSS

$mysterious-blue: #427f8a;
$mysterious-blue-rgb: 66, 127, 138;
$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);
}