#0F73DC

CSS

:root {
  --fading-night: #0f73dc;
  --fading-night-rgb: 15 115 220;
  --fading-night-oklch: oklch(0.563 0.181 255.3);
}

.element {
  color: var(--fading-night);
  background-color: hsl(211 87% 46%);
  border-color: oklch(0.563 0.181 255.3);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #0f73dc;
  --color-fading-night-50: #d5f8ff;
  --color-fading-night-100: #c2ebff;
  --color-fading-night-200: #a3d7ff;
  --color-fading-night-300: #7ab9ff;
  --color-fading-night-400: #4c9fff;
  --color-fading-night-500: #1383fa;
  --color-fading-night-600: #1570d2;
  --color-fading-night-700: #1259a9;
  --color-fading-night-800: #01427e;
  --color-fading-night-900: #022e59;
  --color-fading-night-950: #001a3d;
}

SCSS

$fading-night: #0f73dc;
$fading-night-rgb: 15, 115, 220;
$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);
}