#151228

CSS

:root {
  --dark-knight: #151228;
  --dark-knight-rgb: 21 18 40;
  --dark-knight-oklch: oklch(0.199 0.043 288.1);
}

.element {
  color: var(--dark-knight);
  background-color: hsl(248 38% 11%);
  border-color: oklch(0.199 0.043 288.1);
}

Tailwind CSS v4

@theme {
  --color-dark-knight: #151228;
  --color-dark-knight-50: #f5f3ff;
  --color-dark-knight-100: #e7e6f6;
  --color-dark-knight-200: #d3d2e6;
  --color-dark-knight-300: #b6b4cd;
  --color-dark-knight-400: #9d9bb7;
  --color-dark-knight-500: #8482a2;
  --color-dark-knight-600: #706e89;
  --color-dark-knight-700: #59586e;
  --color-dark-knight-800: #414051;
  --color-dark-knight-900: #2d2c38;
  --color-dark-knight-950: #1a1923;
}

SCSS

$dark-knight: #151228;
$dark-knight-rgb: 21, 18, 40;
$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);
}