#040914

CSS

:root {
  --dark-rift: #040914;
  --dark-rift-rgb: 4 9 20;
  --dark-rift-oklch: oklch(0.14 0.027 260.2);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(221 67% 5%);
  border-color: oklch(0.14 0.027 260.2);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #040914;
  --color-dark-rift-50: #f1f5fd;
  --color-dark-rift-100: #e3e8f1;
  --color-dark-rift-200: #ced5e0;
  --color-dark-rift-300: #b0b8c5;
  --color-dark-rift-400: #959faf;
  --color-dark-rift-500: #7c8798;
  --color-dark-rift-600: #697281;
  --color-dark-rift-700: #545b67;
  --color-dark-rift-800: #3d434c;
  --color-dark-rift-900: #2a2e35;
  --color-dark-rift-950: #171b20;
}

SCSS

$dark-rift: #040914;
$dark-rift-rgb: 4, 9, 20;
$dark-rift-light: mix(#fff, $dark-rift, 20%);
$dark-rift-dark: mix(#000, $dark-rift, 20%);

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