#166FB8

CSS

:root {
  --french-blue: #166fb8;
  --french-blue-rgb: 22 111 184;
  --french-blue-oklch: oklch(0.531 0.139 249.5);
}

.element {
  color: var(--french-blue);
  background-color: hsl(207 79% 40%);
  border-color: oklch(0.531 0.139 249.5);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #166fb8;
  --color-french-blue-50: #d9f9ff;
  --color-french-blue-100: #c7ecff;
  --color-french-blue-200: #a9d9ff;
  --color-french-blue-300: #81bcfc;
  --color-french-blue-400: #58a3ed;
  --color-french-blue-500: #2a8add;
  --color-french-blue-600: #2675bb;
  --color-french-blue-700: #1f5e96;
  --color-french-blue-800: #10456f;
  --color-french-blue-900: #0a304e;
  --color-french-blue-950: #001c34;
}

SCSS

$french-blue: #166fb8;
$french-blue-rgb: 22, 111, 184;
$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);
}