#0A70B6

CSS

:root {
  --french-blue: #0a70b6;
  --french-blue-rgb: 10 112 182;
  --french-blue-oklch: oklch(0.531 0.137 247.3);
}

.element {
  color: var(--french-blue);
  background-color: hsl(204 90% 38%);
  border-color: oklch(0.531 0.137 247.3);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #0a70b6;
  --color-french-blue-50: #d8f9ff;
  --color-french-blue-100: #c5ecff;
  --color-french-blue-200: #a7daff;
  --color-french-blue-300: #7fbdfb;
  --color-french-blue-400: #54a5eb;
  --color-french-blue-500: #228bdb;
  --color-french-blue-600: #2076b9;
  --color-french-blue-700: #1a5e94;
  --color-french-blue-800: #0b466e;
  --color-french-blue-900: #07304e;
  --color-french-blue-950: #001c33;
}

SCSS

$french-blue: #0a70b6;
$french-blue-rgb: 10, 112, 182;
$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);
}