#3F78C0

CSS

:root {
  --fading-night: #3f78c0;
  --fading-night-rgb: 63 120 192;
  --fading-night-oklch: oklch(0.569 0.127 255.3);
}

.element {
  color: var(--fading-night);
  background-color: hsl(213 51% 50%);
  border-color: oklch(0.569 0.127 255.3);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3f78c0;
  --color-fading-night-50: #dff7ff;
  --color-fading-night-100: #ceeaff;
  --color-fading-night-200: #b2d7ff;
  --color-fading-night-300: #8ebaf8;
  --color-fading-night-400: #6aa1e8;
  --color-fading-night-500: #4787d8;
  --color-fading-night-600: #3d73b6;
  --color-fading-night-700: #305c93;
  --color-fading-night-800: #1f446d;
  --color-fading-night-900: #152f4d;
  --color-fading-night-950: #061b33;
}

SCSS

$fading-night: #3f78c0;
$fading-night-rgb: 63, 120, 192;
$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);
}