#296E8A

CSS

:root {
  --chill-of-the-night: #296e8a;
  --chill-of-the-night-rgb: 41 110 138;
  --chill-of-the-night-oklch: oklch(0.507 0.081 228.5);
}

.element {
  color: var(--chill-of-the-night);
  background-color: hsl(197 54% 35%);
  border-color: oklch(0.507 0.081 228.5);
}

Tailwind CSS v4

@theme {
  --color-chill-of-the-night: #296e8a;
  --color-chill-of-the-night-50: #dffaff;
  --color-chill-of-the-night-100: #ceeefe;
  --color-chill-of-the-night-200: #b2dbf1;
  --color-chill-of-the-night-300: #8dc0d9;
  --color-chill-of-the-night-400: #69a8c5;
  --color-chill-of-the-night-500: #4590b1;
  --color-chill-of-the-night-600: #3b7a95;
  --color-chill-of-the-night-700: #2f6278;
  --color-chill-of-the-night-800: #204858;
  --color-chill-of-the-night-900: #15323d;
  --color-chill-of-the-night-950: #061e27;
}

SCSS

$chill-of-the-night: #296e8a;
$chill-of-the-night-rgb: 41, 110, 138;
$chill-of-the-night-light: mix(#fff, $chill-of-the-night, 20%);
$chill-of-the-night-dark: mix(#000, $chill-of-the-night, 20%);

.element {
  color: $chill-of-the-night;
  box-shadow: 0 0 0 2px rgba($chill-of-the-night, 0.35);
}