#4378BB

CSS

:root {
  --fading-night: #4378bb;
  --fading-night-rgb: 67 120 187;
  --fading-night-oklch: oklch(0.567 0.119 255.2);
}

.element {
  color: var(--fading-night);
  background-color: hsl(214 47% 50%);
  border-color: oklch(0.567 0.119 255.2);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #4378bb;
  --color-fading-night-50: #e0f7ff;
  --color-fading-night-100: #cfeaff;
  --color-fading-night-200: #b4d7ff;
  --color-fading-night-300: #91baf4;
  --color-fading-night-400: #6da1e3;
  --color-fading-night-500: #4c88d3;
  --color-fading-night-600: #4173b2;
  --color-fading-night-700: #345c8f;
  --color-fading-night-800: #22446a;
  --color-fading-night-900: #172f4b;
  --color-fading-night-950: #081b31;
}

SCSS

$fading-night: #4378bb;
$fading-night-rgb: 67, 120, 187;
$fading-night-light: mix(#fff, $fading-night, 20%);
$fading-night-dark: mix(#000, $fading-night, 20%);

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