#15152C

CSS

:root {
  --dark-knight: #15152c;
  --dark-knight-rgb: 21 21 44;
  --dark-knight-oklch: oklch(0.209 0.045 281.8);
}

.element {
  color: var(--dark-knight);
  background-color: hsl(240 35% 13%);
  border-color: oklch(0.209 0.045 281.8);
}

Tailwind CSS v4

@theme {
  --color-dark-knight: #15152c;
  --color-dark-knight-50: #f3f4ff;
  --color-dark-knight-100: #e5e6f7;
  --color-dark-knight-200: #d1d2e7;
  --color-dark-knight-300: #b4b5ce;
  --color-dark-knight-400: #9a9cb9;
  --color-dark-knight-500: #8183a4;
  --color-dark-knight-600: #6d6f8a;
  --color-dark-knight-700: #57596f;
  --color-dark-knight-800: #3f4152;
  --color-dark-knight-900: #2b2d39;
  --color-dark-knight-950: #191a23;
}

SCSS

$dark-knight: #15152c;
$dark-knight-rgb: 21, 21, 44;
$dark-knight-light: mix(#fff, $dark-knight, 20%);
$dark-knight-dark: mix(#000, $dark-knight, 20%);

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