#3177CA

CSS

:root {
  --fading-night: #3177ca;
  --fading-night-rgb: 49 119 202;
  --fading-night-oklch: oklch(0.567 0.146 254.8);
}

.element {
  color: var(--fading-night);
  background-color: hsl(213 61% 49%);
  border-color: oklch(0.567 0.146 254.8);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3177ca;
  --color-fading-night-50: #dbf8ff;
  --color-fading-night-100: #c9eaff;
  --color-fading-night-200: #acd7ff;
  --color-fading-night-300: #86baff;
  --color-fading-night-400: #5fa1f3;
  --color-fading-night-500: #3887e4;
  --color-fading-night-600: #3172c0;
  --color-fading-night-700: #275b9b;
  --color-fading-night-800: #164373;
  --color-fading-night-900: #0e2f51;
  --color-fading-night-950: #021b36;
}

SCSS

$fading-night: #3177ca;
$fading-night-rgb: 49, 119, 202;
$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);
}