#0E005E

CSS

:root {
  --the-vast-of-night: #0e005e;
  --the-vast-of-night-rgb: 14 0 94;
  --the-vast-of-night-oklch: oklch(0.226 0.146 271.8);
}

.element {
  color: var(--the-vast-of-night);
  background-color: hsl(249 100% 18%);
  border-color: oklch(0.226 0.146 271.8);
}

Tailwind CSS v4

@theme {
  --color-the-vast-of-night: #0e005e;
  --color-the-vast-of-night-50: #e7f3ff;
  --color-the-vast-of-night-100: #d8e5ff;
  --color-the-vast-of-night-200: #c0d0ff;
  --color-the-vast-of-night-300: #a0b2ff;
  --color-the-vast-of-night-400: #8097f4;
  --color-the-vast-of-night-500: #657ce6;
  --color-the-vast-of-night-600: #5669c2;
  --color-the-vast-of-night-700: #44549c;
  --color-the-vast-of-night-800: #2f3e74;
  --color-the-vast-of-night-900: #202b52;
  --color-the-vast-of-night-950: #101837;
}

SCSS

$the-vast-of-night: #0e005e;
$the-vast-of-night-rgb: 14, 0, 94;
$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);
}