#2970AB

CSS

:root {
  --french-blue: #2970ab;
  --french-blue-rgb: 41 112 171;
  --french-blue-oklch: oklch(0.53 0.116 247.5);
}

.element {
  color: var(--french-blue);
  background-color: hsl(207 61% 42%);
  border-color: oklch(0.53 0.116 247.5);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #2970ab;
  --color-french-blue-50: #ddf9ff;
  --color-french-blue-100: #cbecff;
  --color-french-blue-200: #afd9ff;
  --color-french-blue-300: #89bcf1;
  --color-french-blue-400: #63a4e0;
  --color-french-blue-500: #3d8bcf;
  --color-french-blue-600: #3576ae;
  --color-french-blue-700: #2a5e8c;
  --color-french-blue-800: #1a4668;
  --color-french-blue-900: #113049;
  --color-french-blue-950: #041c30;
}

SCSS

$french-blue: #2970ab;
$french-blue-rgb: 41, 112, 171;
$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);
}