#1C152A

CSS

:root {
  --dark-knight: #1c152a;
  --dark-knight-rgb: 28 21 42;
  --dark-knight-oklch: oklch(0.216 0.041 298.2);
}

.element {
  color: var(--dark-knight);
  background-color: hsl(260 33% 12%);
  border-color: oklch(0.216 0.041 298.2);
}

Tailwind CSS v4

@theme {
  --color-dark-knight: #1c152a;
  --color-dark-knight-50: #f7f3ff;
  --color-dark-knight-100: #eae5f4;
  --color-dark-knight-200: #d7d1e4;
  --color-dark-knight-300: #bab3ca;
  --color-dark-knight-400: #a19ab4;
  --color-dark-knight-500: #89819e;
  --color-dark-knight-600: #746d86;
  --color-dark-knight-700: #5d576b;
  --color-dark-knight-800: #43404f;
  --color-dark-knight-900: #2f2c37;
  --color-dark-knight-950: #1b1922;
}

SCSS

$dark-knight: #1c152a;
$dark-knight-rgb: 28, 21, 42;
$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);
}