#0A0D15

CSS

:root {
  --dark-rift: #0a0d15;
  --dark-rift-rgb: 10 13 21;
  --dark-rift-oklch: oklch(0.16 0.018 268.5);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(224 35% 6%);
  border-color: oklch(0.16 0.018 268.5);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #0a0d15;
  --color-dark-rift-50: #f3f5fa;
  --color-dark-rift-100: #e5e8ee;
  --color-dark-rift-200: #d1d4dc;
  --color-dark-rift-300: #b4b7c1;
  --color-dark-rift-400: #9a9ea9;
  --color-dark-rift-500: #818692;
  --color-dark-rift-600: #6d717c;
  --color-dark-rift-700: #575b63;
  --color-dark-rift-800: #3f4249;
  --color-dark-rift-900: #2c2e32;
  --color-dark-rift-950: #191b1e;
}

SCSS

$dark-rift: #0a0d15;
$dark-rift-rgb: 10, 13, 21;
$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);
}