#4578BC

CSS

:root {
  --fading-night: #4578bc;
  --fading-night-rgb: 69 120 188;
  --fading-night-oklch: oklch(0.569 0.119 256.2);
}

.element {
  color: var(--fading-night);
  background-color: hsl(214 47% 50%);
  border-color: oklch(0.569 0.119 256.2);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #4578bc;
  --color-fading-night-50: #e1f7ff;
  --color-fading-night-100: #d0eaff;
  --color-fading-night-200: #b5d6ff;
  --color-fading-night-300: #92b9f4;
  --color-fading-night-400: #6fa1e4;
  --color-fading-night-500: #4e87d4;
  --color-fading-night-600: #4373b3;
  --color-fading-night-700: #355c8f;
  --color-fading-night-800: #23436b;
  --color-fading-night-900: #172f4b;
  --color-fading-night-950: #081b31;
}

SCSS

$fading-night: #4578bc;
$fading-night-rgb: 69, 120, 188;
$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);
}