#0F70B6

CSS

:root {
  --french-blue: #0f70b6;
  --french-blue-rgb: 15 112 182;
  --french-blue-oklch: oklch(0.531 0.136 247.6);
}

.element {
  color: var(--french-blue);
  background-color: hsl(205 85% 39%);
  border-color: oklch(0.531 0.136 247.6);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #0f70b6;
  --color-french-blue-50: #d8f9ff;
  --color-french-blue-100: #c6ecff;
  --color-french-blue-200: #a8d9ff;
  --color-french-blue-300: #80bdfb;
  --color-french-blue-400: #56a4ea;
  --color-french-blue-500: #258bdb;
  --color-french-blue-600: #2376b9;
  --color-french-blue-700: #1c5e94;
  --color-french-blue-800: #0d466e;
  --color-french-blue-900: #08304e;
  --color-french-blue-950: #001c33;
}

SCSS

$french-blue: #0f70b6;
$french-blue-rgb: 15, 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);
}