#101532

CSS

:root {
  --dark-knight: #101532;
  --dark-knight-rgb: 16 21 50;
  --dark-knight-oklch: oklch(0.209 0.057 273.1);
}

.element {
  color: var(--dark-knight);
  background-color: hsl(231 52% 13%);
  border-color: oklch(0.209 0.057 273.1);
}

Tailwind CSS v4

@theme {
  --color-dark-knight: #101532;
  --color-dark-knight-50: #f0f4ff;
  --color-dark-knight-100: #e2e7fc;
  --color-dark-knight-200: #cdd3ed;
  --color-dark-knight-300: #aeb6d5;
  --color-dark-knight-400: #939dc1;
  --color-dark-knight-500: #7984ad;
  --color-dark-knight-600: #677092;
  --color-dark-knight-700: #525975;
  --color-dark-knight-800: #3b4157;
  --color-dark-knight-900: #282d3c;
  --color-dark-knight-950: #161a26;
}

SCSS

$dark-knight: #101532;
$dark-knight-rgb: 16, 21, 50;
$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);
}