#3B4B97

CSS

:root {
  --queen-of-the-night-shift: #3b4b97;
  --queen-of-the-night-shift-rgb: 59 75 151;
  --queen-of-the-night-shift-oklch: oklch(0.441 0.125 271.5);
}

.element {
  color: var(--queen-of-the-night-shift);
  background-color: hsl(230 44% 41%);
  border-color: oklch(0.441 0.125 271.5);
}

Tailwind CSS v4

@theme {
  --color-queen-of-the-night-shift: #3b4b97;
  --color-queen-of-the-night-shift-50: #e9f4ff;
  --color-queen-of-the-night-shift-100: #dae6ff;
  --color-queen-of-the-night-shift-200: #c3d1ff;
  --color-queen-of-the-night-shift-300: #a3b3f8;
  --color-queen-of-the-night-shift-400: #8499e8;
  --color-queen-of-the-night-shift-500: #697fd9;
  --color-queen-of-the-night-shift-600: #596cb7;
  --color-queen-of-the-night-shift-700: #475693;
  --color-queen-of-the-night-shift-800: #313f6e;
  --color-queen-of-the-night-shift-900: #212c4d;
  --color-queen-of-the-night-shift-950: #111933;
}

SCSS

$queen-of-the-night-shift: #3b4b97;
$queen-of-the-night-shift-rgb: 59, 75, 151;
$queen-of-the-night-shift-light: mix(#fff, $queen-of-the-night-shift, 20%);
$queen-of-the-night-shift-dark: mix(#000, $queen-of-the-night-shift, 20%);

.element {
  color: $queen-of-the-night-shift;
  box-shadow: 0 0 0 2px rgba($queen-of-the-night-shift, 0.35);
}