#3F498A

CSS

:root {
  --queen-of-the-night-shift: #3f498a;
  --queen-of-the-night-shift-rgb: 63 73 138;
  --queen-of-the-night-shift-oklch: oklch(0.431 0.107 274.4);
}

.element {
  color: var(--queen-of-the-night-shift);
  background-color: hsl(232 37% 39%);
  border-color: oklch(0.431 0.107 274.4);
}

Tailwind CSS v4

@theme {
  --color-queen-of-the-night-shift: #3f498a;
  --color-queen-of-the-night-shift-50: #ecf3ff;
  --color-queen-of-the-night-shift-100: #dee6ff;
  --color-queen-of-the-night-shift-200: #c8d1ff;
  --color-queen-of-the-night-shift-300: #a8b3ef;
  --color-queen-of-the-night-shift-400: #8b99de;
  --color-queen-of-the-night-shift-500: #717fcd;
  --color-queen-of-the-night-shift-600: #606cad;
  --color-queen-of-the-night-shift-700: #4c568b;
  --color-queen-of-the-night-shift-800: #363f67;
  --color-queen-of-the-night-shift-900: #252c49;
  --color-queen-of-the-night-shift-950: #131930;
}

SCSS

$queen-of-the-night-shift: #3f498a;
$queen-of-the-night-shift-rgb: 63, 73, 138;
$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);
}