#2874D2

CSS

:root {
  --fading-night: #2874d2;
  --fading-night-rgb: 40 116 210;
  --fading-night-oklch: oklch(0.563 0.162 256);
}

.element {
  color: var(--fading-night);
  background-color: hsl(213 68% 49%);
  border-color: oklch(0.563 0.162 256);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #2874d2;
  --color-fading-night-50: #d9f7ff;
  --color-fading-night-100: #c7eaff;
  --color-fading-night-200: #a9d6ff;
  --color-fading-night-300: #82b9ff;
  --color-fading-night-400: #599ffc;
  --color-fading-night-500: #2f85ee;
  --color-fading-night-600: #2a70c9;
  --color-fading-night-700: #215aa2;
  --color-fading-night-800: #114279;
  --color-fading-night-900: #0b2e55;
  --color-fading-night-950: #001a39;
}

SCSS

$fading-night: #2874d2;
$fading-night-rgb: 40, 116, 210;
$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);
}