#2170AE

CSS

:root {
  --french-blue: #2170ae;
  --french-blue-rgb: 33 112 174;
  --french-blue-oklch: oklch(0.529 0.122 247.1);
}

.element {
  color: var(--french-blue);
  background-color: hsl(206 68% 41%);
  border-color: oklch(0.529 0.122 247.1);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #2170ae;
  --color-french-blue-50: #dbf9ff;
  --color-french-blue-100: #c9ecff;
  --color-french-blue-200: #acd9ff;
  --color-french-blue-300: #85bdf4;
  --color-french-blue-400: #5ea4e3;
  --color-french-blue-500: #358cd2;
  --color-french-blue-600: #2f76b1;
  --color-french-blue-700: #255f8f;
  --color-french-blue-800: #16466a;
  --color-french-blue-900: #0e304a;
  --color-french-blue-950: #021c31;
}

SCSS

$french-blue: #2170ae;
$french-blue-rgb: 33, 112, 174;
$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);
}