#4877BF

CSS

:root {
  --fading-night: #4877bf;
  --fading-night-rgb: 72 119 191;
  --fading-night-oklch: oklch(0.57 0.123 258.7);
}

.element {
  color: var(--fading-night);
  background-color: hsl(216 48% 52%);
  border-color: oklch(0.57 0.123 258.7);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #4877bf;
  --color-fading-night-50: #e1f6ff;
  --color-fading-night-100: #d1e9ff;
  --color-fading-night-200: #b6d6ff;
  --color-fading-night-300: #93b8f7;
  --color-fading-night-400: #719fe7;
  --color-fading-night-500: #5186d7;
  --color-fading-night-600: #4571b5;
  --color-fading-night-700: #375b91;
  --color-fading-night-800: #24436c;
  --color-fading-night-900: #182e4c;
  --color-fading-night-950: #091b32;
}

SCSS

$fading-night: #4877bf;
$fading-night-rgb: 72, 119, 191;
$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);
}