#1974D7

CSS

:root {
  --fading-night: #1974d7;
  --fading-night-rgb: 25 116 215;
  --fading-night-oklch: oklch(0.564 0.172 255);
}

.element {
  color: var(--fading-night);
  background-color: hsl(211 79% 47%);
  border-color: oklch(0.564 0.172 255);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #1974d7;
  --color-fading-night-50: #d6f8ff;
  --color-fading-night-100: #c4ebff;
  --color-fading-night-200: #a5d7ff;
  --color-fading-night-300: #7cb9ff;
  --color-fading-night-400: #50a0ff;
  --color-fading-night-500: #1e84f4;
  --color-fading-night-600: #1d70ce;
  --color-fading-night-700: #175aa5;
  --color-fading-night-800: #06427b;
  --color-fading-night-900: #052e57;
  --color-fading-night-950: #001a3b;
}

SCSS

$fading-night: #1974d7;
$fading-night-rgb: 25, 116, 215;
$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);
}