#2576D6

CSS

:root {
  --fading-night: #2576d6;
  --fading-night-rgb: 37 118 214;
  --fading-night-oklch: oklch(0.57 0.166 255.5);
}

.element {
  color: var(--fading-night);
  background-color: hsl(213 71% 49%);
  border-color: oklch(0.57 0.166 255.5);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #2576d6;
  --color-fading-night-50: #d8f8ff;
  --color-fading-night-100: #c5eaff;
  --color-fading-night-200: #a7d7ff;
  --color-fading-night-300: #80b9ff;
  --color-fading-night-400: #56a0fe;
  --color-fading-night-500: #2985f1;
  --color-fading-night-600: #2571cb;
  --color-fading-night-700: #1d5aa3;
  --color-fading-night-800: #0d427a;
  --color-fading-night-900: #082e56;
  --color-fading-night-950: #001a3a;
}

SCSS

$fading-night: #2576d6;
$fading-night-rgb: 37, 118, 214;
$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);
}