#216CC3

CSS

:root {
  --matt-blue: #216cc3;
  --matt-blue-rgb: 33 108 195;
  --matt-blue-oklch: oklch(0.534 0.154 255.2);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(212 71% 45%);
  border-color: oklch(0.534 0.154 255.2);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #216cc3;
  --color-matt-blue-50: #daf8ff;
  --color-matt-blue-100: #c8eaff;
  --color-matt-blue-200: #aad7ff;
  --color-matt-blue-300: #84b9ff;
  --color-matt-blue-400: #5ca0f7;
  --color-matt-blue-500: #3386e9;
  --color-matt-blue-600: #2d71c4;
  --color-matt-blue-700: #245b9e;
  --color-matt-blue-800: #134376;
  --color-matt-blue-900: #0c2e53;
  --color-matt-blue-950: #011b38;
}

SCSS

$matt-blue: #216cc3;
$matt-blue-rgb: 33, 108, 195;
$matt-blue-light: mix(#fff, $matt-blue, 20%);
$matt-blue-dark: mix(#000, $matt-blue, 20%);

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