#3376C3

CSS

:root {
  --fading-night: #3376c3;
  --fading-night-rgb: 51 118 195;
  --fading-night-oklch: oklch(0.561 0.137 254);
}

.element {
  color: var(--fading-night);
  background-color: hsl(212 59% 48%);
  border-color: oklch(0.561 0.137 254);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3376c3;
  --color-fading-night-50: #dcf8ff;
  --color-fading-night-100: #caebff;
  --color-fading-night-200: #aed7ff;
  --color-fading-night-300: #88bafd;
  --color-fading-night-400: #62a1ee;
  --color-fading-night-500: #3c87de;
  --color-fading-night-600: #3473bb;
  --color-fading-night-700: #295c97;
  --color-fading-night-800: #194470;
  --color-fading-night-900: #102f4f;
  --color-fading-night-950: #031b35;
}

SCSS

$fading-night: #3376c3;
$fading-night-rgb: 51, 118, 195;
$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);
}