#4E70CD

CSS

:root {
  --royal-blue: #4e70cd;
  --royal-blue-rgb: 78 112 205;
  --royal-blue-oklch: oklch(0.566 0.149 266.6);
}

.element {
  color: var(--royal-blue);
  background-color: hsl(224 56% 55%);
  border-color: oklch(0.566 0.149 266.6);
}

Tailwind CSS v4

@theme {
  --color-royal-blue: #4e70cd;
  --color-royal-blue-50: #e3f4ff;
  --color-royal-blue-100: #d3e7ff;
  --color-royal-blue-200: #bad2ff;
  --color-royal-blue-300: #98b4ff;
  --color-royal-blue-400: #769af6;
  --color-royal-blue-500: #597fe8;
  --color-royal-blue-600: #4b6cc3;
  --color-royal-blue-700: #3c569d;
  --color-royal-blue-800: #283f75;
  --color-royal-blue-900: #1b2c53;
  --color-royal-blue-950: #0b1938;
}

SCSS

$royal-blue: #4e70cd;
$royal-blue-rgb: 78, 112, 205;
$royal-blue-light: mix(#fff, $royal-blue, 20%);
$royal-blue-dark: mix(#000, $royal-blue, 20%);

.element {
  color: $royal-blue;
  box-shadow: 0 0 0 2px rgba($royal-blue, 0.35);
}