#21313E

CSS

:root {
  --blue-whale: #21313e;
  --blue-whale-rgb: 33 49 62;
  --blue-whale-oklch: oklch(0.305 0.032 243.6);
}

.element {
  color: var(--blue-whale);
  background-color: hsl(207 31% 19%);
  border-color: oklch(0.305 0.032 243.6);
}

Tailwind CSS v4

@theme {
  --color-blue-whale: #21313e;
  --color-blue-whale-50: #eef6fe;
  --color-blue-whale-100: #e0e9f2;
  --color-blue-whale-200: #cad6e1;
  --color-blue-whale-300: #abb9c7;
  --color-blue-whale-400: #8fa1b0;
  --color-blue-whale-500: #75899a;
  --color-blue-whale-600: #637482;
  --color-blue-whale-700: #4f5d68;
  --color-blue-whale-800: #39444d;
  --color-blue-whale-900: #272f35;
  --color-blue-whale-950: #151b20;
}

SCSS

$blue-whale: #21313e;
$blue-whale-rgb: 33, 49, 62;
$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);
}