#3B4691

CSS

:root {
  --queen-of-the-night-shift: #3b4691;
  --queen-of-the-night-shift-rgb: 59 70 145;
  --queen-of-the-night-shift-oklch: oklch(0.426 0.123 273.7);
}

.element {
  color: var(--queen-of-the-night-shift);
  background-color: hsl(232 42% 40%);
  border-color: oklch(0.426 0.123 273.7);
}

Tailwind CSS v4

@theme {
  --color-queen-of-the-night-shift: #3b4691;
  --color-queen-of-the-night-shift-50: #ebf3ff;
  --color-queen-of-the-night-shift-100: #dce5ff;
  --color-queen-of-the-night-shift-200: #c5d1ff;
  --color-queen-of-the-night-shift-300: #a6b2f7;
  --color-queen-of-the-night-shift-400: #8898e7;
  --color-queen-of-the-night-shift-500: #6d7ed7;
  --color-queen-of-the-night-shift-600: #5c6bb5;
  --color-queen-of-the-night-shift-700: #4a5592;
  --color-queen-of-the-night-shift-800: #333f6d;
  --color-queen-of-the-night-shift-900: #232b4d;
  --color-queen-of-the-night-shift-950: #121833;
}

SCSS

$queen-of-the-night-shift: #3b4691;
$queen-of-the-night-shift-rgb: 59, 70, 145;
$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);
}