#253748

CSS

:root {
  --blue-whale: #253748;
  --blue-whale-rgb: 37 55 72;
  --blue-whale-oklch: oklch(0.329 0.038 247.6);
}

.element {
  color: var(--blue-whale);
  background-color: hsl(209 32% 21%);
  border-color: oklch(0.329 0.038 247.6);
}

Tailwind CSS v4

@theme {
  --color-blue-whale: #253748;
  --color-blue-whale-50: #edf6ff;
  --color-blue-whale-100: #dfe9f5;
  --color-blue-whale-200: #c8d6e4;
  --color-blue-whale-300: #a9b9cb;
  --color-blue-whale-400: #8da1b4;
  --color-blue-whale-500: #72899f;
  --color-blue-whale-600: #617486;
  --color-blue-whale-700: #4d5d6c;
  --color-blue-whale-800: #38444f;
  --color-blue-whale-900: #262f37;
  --color-blue-whale-950: #141b22;
}

SCSS

$blue-whale: #253748;
$blue-whale-rgb: 37, 55, 72;
$blue-whale-light: mix(#fff, $blue-whale, 20%);
$blue-whale-dark: mix(#000, $blue-whale, 20%);

.element {
  color: $blue-whale;
  box-shadow: 0 0 0 2px rgba($blue-whale, 0.35);
}