#0C2669

CSS

:root {
  --dark-sapphire: #0c2669;
  --dark-sapphire-rgb: 12 38 105;
  --dark-sapphire-oklch: oklch(0.299 0.122 264.1);
}

.element {
  color: var(--dark-sapphire);
  background-color: hsl(223 79% 23%);
  border-color: oklch(0.299 0.122 264.1);
}

Tailwind CSS v4

@theme {
  --color-dark-sapphire: #0c2669;
  --color-dark-sapphire-50: #e5f5ff;
  --color-dark-sapphire-100: #d5e8ff;
  --color-dark-sapphire-200: #bcd4ff;
  --color-dark-sapphire-300: #9ab6f6;
  --color-dark-sapphire-400: #7a9de6;
  --color-dark-sapphire-500: #5c83d6;
  --color-dark-sapphire-600: #4f6fb5;
  --color-dark-sapphire-700: #3f5991;
  --color-dark-sapphire-800: #2b416c;
  --color-dark-sapphire-900: #1d2d4c;
  --color-dark-sapphire-950: #0d1a32;
}

SCSS

$dark-sapphire: #0c2669;
$dark-sapphire-rgb: 12, 38, 105;
$dark-sapphire-light: mix(#fff, $dark-sapphire, 20%);
$dark-sapphire-dark: mix(#000, $dark-sapphire, 20%);

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