#1D75D3

CSS

:root {
  --fading-night: #1d75d3;
  --fading-night-rgb: 29 117 211;
  --fading-night-oklch: oklch(0.564 0.165 254.3);
}

.element {
  color: var(--fading-night);
  background-color: hsl(211 76% 47%);
  border-color: oklch(0.564 0.165 254.3);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #1d75d3;
  --color-fading-night-50: #d7f8ff;
  --color-fading-night-100: #c4ebff;
  --color-fading-night-200: #a6d7ff;
  --color-fading-night-300: #7ebaff;
  --color-fading-night-400: #53a0fd;
  --color-fading-night-500: #2286ef;
  --color-fading-night-600: #2071ca;
  --color-fading-night-700: #1a5ba2;
  --color-fading-night-800: #094379;
  --color-fading-night-900: #062e55;
  --color-fading-night-950: #001a3a;
}

SCSS

$fading-night: #1d75d3;
$fading-night-rgb: 29, 117, 211;
$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);
}