#596CE0

CSS

:root {
  --royal-blue: #596ce0;
  --royal-blue-rgb: 89 108 224;
  --royal-blue-oklch: oklch(0.578 0.176 272.7);
}

.element {
  color: var(--royal-blue);
  background-color: hsl(232 69% 61%);
  border-color: oklch(0.578 0.176 272.7);
}

Tailwind CSS v4

@theme {
  --color-royal-blue: #596ce0;
  --color-royal-blue-50: #e5f2ff;
  --color-royal-blue-100: #d6e4ff;
  --color-royal-blue-200: #becfff;
  --color-royal-blue-300: #9dafff;
  --color-royal-blue-400: #7d94ff;
  --color-royal-blue-500: #6277f9;
  --color-royal-blue-600: #5365d2;
  --color-royal-blue-700: #4251a9;
  --color-royal-blue-800: #2c3b7e;
  --color-royal-blue-900: #1e2959;
  --color-royal-blue-950: #0e163d;
}

SCSS

$royal-blue: #596ce0;
$royal-blue-rgb: 89, 108, 224;
$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);
}