#2670AF

CSS

:root {
  --french-blue: #2670af;
  --french-blue-rgb: 38 112 175;
  --french-blue-oklch: oklch(0.531 0.122 248.4);
}

.element {
  color: var(--french-blue);
  background-color: hsl(208 64% 42%);
  border-color: oklch(0.531 0.122 248.4);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #2670af;
  --color-french-blue-50: #dcf9ff;
  --color-french-blue-100: #caecff;
  --color-french-blue-200: #add9ff;
  --color-french-blue-300: #87bcf4;
  --color-french-blue-400: #61a4e3;
  --color-french-blue-500: #398bd3;
  --color-french-blue-600: #3276b2;
  --color-french-blue-700: #285e8f;
  --color-french-blue-800: #18456a;
  --color-french-blue-900: #10304b;
  --color-french-blue-950: #031c31;
}

SCSS

$french-blue: #2670af;
$french-blue-rgb: 38, 112, 175;
$french-blue-light: mix(#fff, $french-blue, 20%);
$french-blue-dark: mix(#000, $french-blue, 20%);

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