Night Blue

CSS

:root {
  --night-blue: #040348;
  --night-blue-rgb: 4 3 72;
  --night-blue-oklch: oklch(0.191 0.12 267.8);
}

.element {
  color: var(--night-blue);
  background-color: hsl(241 92% 15%);
  border-color: oklch(0.191 0.12 267.8);
}

Tailwind CSS v4

@theme {
  --color-night-blue: #040348;
  --color-night-blue-50: #e7f4ff;
  --color-night-blue-100: #d8e7ff;
  --color-night-blue-200: #c0d3ff;
  --color-night-blue-300: #9fb5f5;
  --color-night-blue-400: #809be5;
  --color-night-blue-500: #6481d5;
  --color-night-blue-600: #556eb4;
  --color-night-blue-700: #435891;
  --color-night-blue-800: #2f406c;
  --color-night-blue-900: #1f2c4c;
  --color-night-blue-950: #0f1932;
}

SCSS

$night-blue: #040348;
$night-blue-rgb: 4, 3, 72;
$night-blue-light: mix(#fff, $night-blue, 20%);
$night-blue-dark: mix(#000, $night-blue, 20%);

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