#2570AC

CSS

:root {
  --french-blue: #2570ac;
  --french-blue-rgb: 37 112 172;
  --french-blue-oklch: oklch(0.529 0.119 247);
}

.element {
  color: var(--french-blue);
  background-color: hsl(207 65% 41%);
  border-color: oklch(0.529 0.119 247);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #2570ac;
  --color-french-blue-50: #dcf9ff;
  --color-french-blue-100: #caecff;
  --color-french-blue-200: #add9ff;
  --color-french-blue-300: #87bdf2;
  --color-french-blue-400: #61a4e1;
  --color-french-blue-500: #398cd0;
  --color-french-blue-600: #3276b0;
  --color-french-blue-700: #275f8d;
  --color-french-blue-800: #184668;
  --color-french-blue-900: #103049;
  --color-french-blue-950: #031c30;
}

SCSS

$french-blue: #2570ac;
$french-blue-rgb: 37, 112, 172;
$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);
}