#2174D5

CSS

:root {
  --fading-night: #2174d5;
  --fading-night-rgb: 33 116 213;
  --fading-night-oklch: oklch(0.564 0.168 255.5);
}

.element {
  color: var(--fading-night);
  background-color: hsl(212 73% 48%);
  border-color: oklch(0.564 0.168 255.5);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #2174d5;
  --color-fading-night-50: #d7f8ff;
  --color-fading-night-100: #c5eaff;
  --color-fading-night-200: #a7d7ff;
  --color-fading-night-300: #7fb9ff;
  --color-fading-night-400: #55a0ff;
  --color-fading-night-500: #2784f2;
  --color-fading-night-600: #2470cc;
  --color-fading-night-700: #1c5aa4;
  --color-fading-night-800: #0c427a;
  --color-fading-night-900: #072e56;
  --color-fading-night-950: #001a3a;
}

SCSS

$fading-night: #2174d5;
$fading-night-rgb: 33, 116, 213;
$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);
}