#1F75D2

CSS

:root {
  --fading-night: #1f75d2;
  --fading-night-rgb: 31 117 210;
  --fading-night-oklch: oklch(0.563 0.163 254.3);
}

.element {
  color: var(--fading-night);
  background-color: hsl(211 74% 47%);
  border-color: oklch(0.563 0.163 254.3);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #1f75d2;
  --color-fading-night-50: #d7f8ff;
  --color-fading-night-100: #c5ebff;
  --color-fading-night-200: #a7d7ff;
  --color-fading-night-300: #7fbaff;
  --color-fading-night-400: #54a0fc;
  --color-fading-night-500: #2586ee;
  --color-fading-night-600: #2271c9;
  --color-fading-night-700: #1b5ba2;
  --color-fading-night-800: #0b4378;
  --color-fading-night-900: #072e55;
  --color-fading-night-950: #001b39;
}

SCSS

$fading-night: #1f75d2;
$fading-night-rgb: 31, 117, 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);
}