#0B025D

CSS

:root {
  --the-vast-of-night: #0b025d;
  --the-vast-of-night-rgb: 11 2 93;
  --the-vast-of-night-oklch: oklch(0.225 0.144 270.1);
}

.element {
  color: var(--the-vast-of-night);
  background-color: hsl(246 96% 19%);
  border-color: oklch(0.225 0.144 270.1);
}

Tailwind CSS v4

@theme {
  --color-the-vast-of-night: #0b025d;
  --color-the-vast-of-night-50: #e6f4ff;
  --color-the-vast-of-night-100: #d7e6ff;
  --color-the-vast-of-night-200: #bfd1ff;
  --color-the-vast-of-night-300: #9eb3ff;
  --color-the-vast-of-night-400: #7e99f3;
  --color-the-vast-of-night-500: #627de5;
  --color-the-vast-of-night-600: #536ac1;
  --color-the-vast-of-night-700: #42559b;
  --color-the-vast-of-night-800: #2d3f74;
  --color-the-vast-of-night-900: #1e2b52;
  --color-the-vast-of-night-950: #0f1837;
}

SCSS

$the-vast-of-night: #0b025d;
$the-vast-of-night-rgb: 11, 2, 93;
$the-vast-of-night-light: mix(#fff, $the-vast-of-night, 20%);
$the-vast-of-night-dark: mix(#000, $the-vast-of-night, 20%);

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