#005794

CSS

:root {
  --dark-denim: #005794;
  --dark-denim-rgb: 0 87 148;
  --dark-denim-oklch: oklch(0.447 0.122 248.6);
}

.element {
  color: var(--dark-denim);
  background-color: hsl(205 100% 29%);
  border-color: oklch(0.447 0.122 248.6);
}

Tailwind CSS v4

@theme {
  --color-dark-denim: #005794;
  --color-dark-denim-50: #dcf9ff;
  --color-dark-denim-100: #caecff;
  --color-dark-denim-200: #add9ff;
  --color-dark-denim-300: #87bcf4;
  --color-dark-denim-400: #61a4e3;
  --color-dark-denim-500: #3a8bd3;
  --color-dark-denim-600: #3276b2;
  --color-dark-denim-700: #285e8f;
  --color-dark-denim-800: #18456a;
  --color-dark-denim-900: #10304a;
  --color-dark-denim-950: #031c31;
}

SCSS

$dark-denim: #005794;
$dark-denim-rgb: 0, 87, 148;
$dark-denim-light: mix(#fff, $dark-denim, 20%);
$dark-denim-dark: mix(#000, $dark-denim, 20%);

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